{"id":287,"date":"2021-03-25T03:03:01","date_gmt":"2021-03-25T03:03:01","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/calculus2\/?post_type=chapter&#038;p=287"},"modified":"2021-11-17T03:05:51","modified_gmt":"2021-11-17T03:05:51","slug":"putting-it-together-sequences-and-series","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/calculus2\/chapter\/putting-it-together-sequences-and-series\/","title":{"raw":"Putting It Together: Sequences and Series","rendered":"Putting It Together: Sequences and Series"},"content":{"raw":"<h3>Finding the Area of the Koch Snowflake<\/h3>\r\n<div id=\"fs-id1169738082467\" data-type=\"problem\">\r\n<p id=\"fs-id1169738082472\">Define a sequence of figures [latex]\\left\\{{F}_{n}\\right\\}[\/latex] recursively as follows in the figure below. Let [latex]{F}_{0}[\/latex] be an equilateral triangle with sides of length [latex]1[\/latex]. For [latex]n\\ge 1[\/latex], let [latex]{F}_{n}[\/latex] be the curve created by removing the middle third of each side of [latex]{F}_{n - 1}[\/latex] and replacing it with an equilateral triangle pointing outward. The limiting figure as [latex]n\\to \\infty [\/latex] is known as <span class=\"no-emphasis\" data-type=\"term\">Koch\u2019s snowflake<\/span>.<\/p>\r\n\r\n<figure id=\"CNX_Calc_Figure_08_00_003\"><figcaption><\/figcaption>[caption id=\"\" align=\"aligncenter\" width=\"899\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4175\/2019\/04\/11234319\/CNX_Calc_Figure_08_00_003.jpg\" alt=\"This is a diagram of the Koch snowflake, which it created through iterations. The base case is an equilateral triangle. In each iteration, the middle third of each line segment is replaced with another equilateral triangle pointing outward.\" width=\"899\" height=\"291\" data-media-type=\"image\/jpeg\" \/> The first four figures, [latex]{F}_{0},{F}_{1},{F}_{2},\\text{and}{F}_{3}[\/latex], in the construction of the Koch snowflake.[\/caption]<\/figure>\r\n<ol id=\"fs-id1169737153597\" type=\"a\">\r\n \t<li>Find the length [latex]{L}_{n}[\/latex] of the perimeter of [latex]{F}_{n}[\/latex]. Evaluate [latex]\\underset{n\\to \\infty }{\\text{lim}}{L}_{n}[\/latex] to find the length of the perimeter of Koch\u2019s snowflake.<\/li>\r\n \t<li>Find the area [latex]{A}_{n}[\/latex] of figure [latex]{F}_{n}[\/latex]. Evaluate [latex]\\underset{n\\to \\infty }{\\text{lim}}{A}_{n}[\/latex] to find the area of Koch\u2019s snowflake.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<h3>Solution<\/h3>\r\n<div id=\"fs-id1169738096042\" data-type=\"solution\">\r\n<ol id=\"fs-id1169738096044\" type=\"a\">\r\n \t<li>Let [latex]{N}_{n}[\/latex] denote the number of sides of figure [latex]{F}_{n}[\/latex]. Since [latex]{F}_{0}[\/latex] is a triangle, [latex]{N}_{0}=3[\/latex]. Let [latex]{l}_{n}[\/latex] denote the length of each side of [latex]{F}_{n}[\/latex]. Since [latex]{F}_{0}[\/latex] is an equilateral triangle with sides of length [latex]{l}_{0}=1[\/latex], we now need to determine [latex]{N}_{1}[\/latex] and [latex]{l}_{1}[\/latex]. Since [latex]{F}_{1}[\/latex] is created by removing the middle third of each side and replacing that line segment with two line segments, for each side of [latex]{F}_{0}[\/latex], we get four sides in [latex]{F}_{1}[\/latex]. Therefore, the number of sides for [latex]{F}_{1}[\/latex] is<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169738079048\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{N}_{1}=4\\cdot 3[\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nSince the length of each of these new line segments is [latex]\\frac{1}{3}[\/latex] the length of the line segments in [latex]{F}_{0}[\/latex], the length of the line segments for [latex]{F}_{1}[\/latex] is given by<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737910109\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{l}_{1}=\\frac{1}{3}\\cdot 1=\\frac{1}{3}[\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nSimilarly, for [latex]{F}_{2}[\/latex], since the middle third of each side of [latex]{F}_{1}[\/latex] is removed and replaced with two line segments, the number of sides in [latex]{F}_{2}[\/latex] is given by<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169738153427\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{N}_{2}=4{N}_{1}=4\\left(4\\cdot 3\\right)={4}^{2}\\cdot 3[\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nSince the length of each of these sides is [latex]\\frac{1}{3}[\/latex] the length of the sides of [latex]{F}_{1}[\/latex], the length of each side of figure [latex]{F}_{2}[\/latex] is given by<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737392622\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{l}_{2}=\\frac{1}{3}\\cdot {l}_{1}=\\frac{1}{3}\\cdot \\frac{1}{3}={\\left(\\frac{1}{3}\\right)}^{2}[\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nMore generally, since [latex]{F}_{n}[\/latex] is created by removing the middle third of each side of [latex]{F}_{n - 1}[\/latex] and replacing that line segment with two line segments of length [latex]\\frac{1}{3}{l}_{n - 1}[\/latex] in the shape of an equilateral triangle, we know that [latex]{N}_{n}=4{N}_{n - 1}[\/latex] and [latex]{l}_{n}=\\frac{{l}_{n - 1}}{3}[\/latex]. Therefore, the number of sides of figure [latex]{F}_{n}[\/latex] is<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737933391\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{N}_{n}={4}^{n}\\cdot 3[\/latex]<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nand the length of each side is<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737392573\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{l}_{n}={\\left(\\frac{1}{3}\\right)}^{n}[\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nTherefore, to calculate the perimeter of [latex]{F}_{n}[\/latex], we multiply the number of sides [latex]{N}_{n}[\/latex] and the length of each side [latex]{l}_{n}[\/latex]. We conclude that the perimeter of [latex]{F}_{n}[\/latex] is given by<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737261961\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{L}_{n}={N}_{n}\\cdot {l}_{n}=3\\cdot {\\left(\\frac{4}{3}\\right)}^{n}[\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nTherefore, the length of the perimeter of Koch\u2019s snowflake is<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169738211801\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]L=\\underset{n\\to \\infty }{\\text{lim}}{L}_{n}=\\infty [\/latex].<\/div>\r\n&nbsp;<\/li>\r\n \t<li>Let [latex]{T}_{n}[\/latex] denote the area of each new triangle created when forming [latex]{F}_{n}[\/latex]. For [latex]n=0[\/latex], [latex]{T}_{0}[\/latex] is the area of the original equilateral triangle. Therefore, [latex]{T}_{0}={A}_{0}=\\frac{\\sqrt{3}}{4}[\/latex]. For [latex]n\\ge 1[\/latex], since the lengths of the sides of the new triangle are [latex]\\frac{1}{3}[\/latex] the length of the sides of [latex]{F}_{n - 1}[\/latex], we have<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169738080336\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{T}_{n}={\\left(\\frac{1}{3}\\right)}^{2}{T}_{n - 1}=\\frac{1}{9}\\cdot {T}_{n - 1}[\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nTherefore, [latex]{T}_{n}={\\left(\\frac{1}{9}\\right)}^{n}\\cdot \\frac{\\sqrt{3}}{4}[\/latex]. Since a new triangle is formed on each side of [latex]{F}_{n - 1}[\/latex], <span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169738088623\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]\\begin{array}{cc}\\hfill {A}_{n}&amp; ={A}_{n - 1}+{N}_{n - 1}\\cdot {T}_{n}\\hfill \\\\ &amp; ={A}_{n - 1}+\\left(3\\cdot {4}^{n - 1}\\right)\\cdot {\\left(\\frac{1}{9}\\right)}^{n}\\cdot \\frac{\\sqrt{3}}{4}\\hfill \\\\ &amp; ={A}_{n - 1}+\\frac{3}{4}\\cdot {\\left(\\frac{4}{9}\\right)}^{n}\\cdot \\frac{\\sqrt{3}}{4}.\\hfill \\end{array}[\/latex]<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nWriting out the first few terms [latex]{A}_{0},{A}_{1},{A}_{2}[\/latex], we see that<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737269810\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]\\begin{array}{}\\\\ {A}_{0}=\\frac{\\sqrt{3}}{4}\\hfill \\\\ {A}_{1}={A}_{0}+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)\\cdot \\frac{\\sqrt{3}}{4}=\\frac{\\sqrt{3}}{4}+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)\\cdot \\frac{\\sqrt{3}}{4}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)\\right]\\hfill \\\\ {A}_{2}={A}_{1}+\\frac{3}{4}\\cdot {\\left(\\frac{4}{9}\\right)}^{2}\\cdot \\frac{\\sqrt{3}}{4}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)\\right]+\\frac{3}{4}\\cdot {\\left(\\frac{4}{9}\\right)}^{2}\\cdot \\frac{\\sqrt{3}}{4}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)+\\frac{3}{4}\\cdot {\\left(\\frac{4}{9}\\right)}^{2}\\right].\\hfill \\end{array}[\/latex]<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nMore generally,<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737226081\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{A}_{n}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{3}{4}\\left(\\frac{4}{9}+{\\left(\\frac{4}{9}\\right)}^{2}+\\cdots +{\\left(\\frac{4}{9}\\right)}^{n}\\right)\\right][\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nFactoring [latex]\\frac{4}{9}[\/latex] out of each term inside the inner parentheses, we rewrite our expression as<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737364353\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{A}_{n}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{1}{3}\\left(1+\\frac{4}{9}+{\\left(\\frac{4}{9}\\right)}^{2}+\\cdots +{\\left(\\frac{4}{9}\\right)}^{n - 1}\\right)\\right][\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nThe expression [latex]1+\\left(\\frac{4}{9}\\right)+{\\left(\\frac{4}{9}\\right)}^{2}+\\cdots +{\\left(\\frac{4}{9}\\right)}^{n - 1}[\/latex] is a geometric sum. As shown earlier, this sum satisfies<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737162064\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]1+\\frac{4}{9}+{\\left(\\frac{4}{9}\\right)}^{2}+\\cdots +{\\left(\\frac{4}{9}\\right)}^{n - 1}=\\frac{1-{\\left(\\frac{4}{9}\\right)}^{n}}{1-\\left(\\frac{4}{9}\\right)}[\/latex].<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nSubstituting this expression into the expression above and simplifying, we conclude that<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169738211851\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]\\begin{array}{cc}\\hfill {A}_{n}&amp; =\\frac{\\sqrt{3}}{4}\\left[1+\\frac{1}{3}\\left(\\frac{1-{\\left(\\frac{4}{9}\\right)}^{n}}{1-\\left(\\frac{4}{9}\\right)}\\right)\\right]\\hfill \\\\ &amp; =\\frac{\\sqrt{3}}{4}\\left[\\frac{8}{5}-\\frac{3}{5}{\\left(\\frac{4}{9}\\right)}^{n}\\right].\\hfill \\end{array}[\/latex]<\/div>\r\n<span data-type=\"newline\">\r\n<\/span>\r\nTherefore, the area of Koch\u2019s snowflake is<span data-type=\"newline\">\r\n<\/span>\r\n<div id=\"fs-id1169737201460\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]A=\\underset{n\\to \\infty }{\\text{lim}}{A}_{n}=\\frac{2\\sqrt{3}}{5}[\/latex].<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n&nbsp;\r\n<h3>Analysis<\/h3>\r\n<div id=\"fs-id1169738216901\" data-type=\"commentary\">\r\n<p id=\"fs-id1169738216906\">The Koch snowflake is interesting because it has finite area, yet infinite perimeter. Although at first this may seem impossible, recall that you have seen similar examples earlier in the text. For example, consider the region bounded by the curve [latex]y=\\frac{1}{{x}^{2}}[\/latex] and the [latex]x[\/latex] -axis on the interval [latex]\\left[1,\\infty \\right)[\/latex]. Since the improper integral<\/p>\r\n\r\n<div id=\"fs-id1169737910330\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{\\displaystyle\\int }_{1}^{\\infty }\\frac{1}{{x}^{2}}dx[\/latex]<\/div>\r\n&nbsp;\r\n<p id=\"fs-id1169737910365\">converges, the area of this region is finite, even though the perimeter is infinite.<\/p>\r\n\r\n<\/div>\r\n<section id=\"fs-id1169737201473\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><\/h3>\r\n<\/section>","rendered":"<h3>Finding the Area of the Koch Snowflake<\/h3>\n<div id=\"fs-id1169738082467\" data-type=\"problem\">\n<p id=\"fs-id1169738082472\">Define a sequence of figures [latex]\\left\\{{F}_{n}\\right\\}[\/latex] recursively as follows in the figure below. Let [latex]{F}_{0}[\/latex] be an equilateral triangle with sides of length [latex]1[\/latex]. For [latex]n\\ge 1[\/latex], let [latex]{F}_{n}[\/latex] be the curve created by removing the middle third of each side of [latex]{F}_{n - 1}[\/latex] and replacing it with an equilateral triangle pointing outward. The limiting figure as [latex]n\\to \\infty[\/latex] is known as <span class=\"no-emphasis\" data-type=\"term\">Koch\u2019s snowflake<\/span>.<\/p>\n<figure id=\"CNX_Calc_Figure_08_00_003\"><figcaption><\/figcaption><div style=\"width: 909px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4175\/2019\/04\/11234319\/CNX_Calc_Figure_08_00_003.jpg\" alt=\"This is a diagram of the Koch snowflake, which it created through iterations. The base case is an equilateral triangle. In each iteration, the middle third of each line segment is replaced with another equilateral triangle pointing outward.\" width=\"899\" height=\"291\" data-media-type=\"image\/jpeg\" \/><\/p>\n<p class=\"wp-caption-text\">The first four figures, [latex]{F}_{0},{F}_{1},{F}_{2},\\text{and}{F}_{3}[\/latex], in the construction of the Koch snowflake.<\/p>\n<\/div>\n<\/figure>\n<ol id=\"fs-id1169737153597\" type=\"a\">\n<li>Find the length [latex]{L}_{n}[\/latex] of the perimeter of [latex]{F}_{n}[\/latex]. Evaluate [latex]\\underset{n\\to \\infty }{\\text{lim}}{L}_{n}[\/latex] to find the length of the perimeter of Koch\u2019s snowflake.<\/li>\n<li>Find the area [latex]{A}_{n}[\/latex] of figure [latex]{F}_{n}[\/latex]. Evaluate [latex]\\underset{n\\to \\infty }{\\text{lim}}{A}_{n}[\/latex] to find the area of Koch\u2019s snowflake.<\/li>\n<\/ol>\n<\/div>\n<h3>Solution<\/h3>\n<div id=\"fs-id1169738096042\" data-type=\"solution\">\n<ol id=\"fs-id1169738096044\" type=\"a\">\n<li>Let [latex]{N}_{n}[\/latex] denote the number of sides of figure [latex]{F}_{n}[\/latex]. Since [latex]{F}_{0}[\/latex] is a triangle, [latex]{N}_{0}=3[\/latex]. Let [latex]{l}_{n}[\/latex] denote the length of each side of [latex]{F}_{n}[\/latex]. Since [latex]{F}_{0}[\/latex] is an equilateral triangle with sides of length [latex]{l}_{0}=1[\/latex], we now need to determine [latex]{N}_{1}[\/latex] and [latex]{l}_{1}[\/latex]. Since [latex]{F}_{1}[\/latex] is created by removing the middle third of each side and replacing that line segment with two line segments, for each side of [latex]{F}_{0}[\/latex], we get four sides in [latex]{F}_{1}[\/latex]. Therefore, the number of sides for [latex]{F}_{1}[\/latex] is<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169738079048\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{N}_{1}=4\\cdot 3[\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nSince the length of each of these new line segments is [latex]\\frac{1}{3}[\/latex] the length of the line segments in [latex]{F}_{0}[\/latex], the length of the line segments for [latex]{F}_{1}[\/latex] is given by<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737910109\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{l}_{1}=\\frac{1}{3}\\cdot 1=\\frac{1}{3}[\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nSimilarly, for [latex]{F}_{2}[\/latex], since the middle third of each side of [latex]{F}_{1}[\/latex] is removed and replaced with two line segments, the number of sides in [latex]{F}_{2}[\/latex] is given by<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169738153427\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{N}_{2}=4{N}_{1}=4\\left(4\\cdot 3\\right)={4}^{2}\\cdot 3[\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nSince the length of each of these sides is [latex]\\frac{1}{3}[\/latex] the length of the sides of [latex]{F}_{1}[\/latex], the length of each side of figure [latex]{F}_{2}[\/latex] is given by<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737392622\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{l}_{2}=\\frac{1}{3}\\cdot {l}_{1}=\\frac{1}{3}\\cdot \\frac{1}{3}={\\left(\\frac{1}{3}\\right)}^{2}[\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nMore generally, since [latex]{F}_{n}[\/latex] is created by removing the middle third of each side of [latex]{F}_{n - 1}[\/latex] and replacing that line segment with two line segments of length [latex]\\frac{1}{3}{l}_{n - 1}[\/latex] in the shape of an equilateral triangle, we know that [latex]{N}_{n}=4{N}_{n - 1}[\/latex] and [latex]{l}_{n}=\\frac{{l}_{n - 1}}{3}[\/latex]. Therefore, the number of sides of figure [latex]{F}_{n}[\/latex] is<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737933391\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{N}_{n}={4}^{n}\\cdot 3[\/latex]<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nand the length of each side is<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737392573\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{l}_{n}={\\left(\\frac{1}{3}\\right)}^{n}[\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nTherefore, to calculate the perimeter of [latex]{F}_{n}[\/latex], we multiply the number of sides [latex]{N}_{n}[\/latex] and the length of each side [latex]{l}_{n}[\/latex]. We conclude that the perimeter of [latex]{F}_{n}[\/latex] is given by<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737261961\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{L}_{n}={N}_{n}\\cdot {l}_{n}=3\\cdot {\\left(\\frac{4}{3}\\right)}^{n}[\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nTherefore, the length of the perimeter of Koch\u2019s snowflake is<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169738211801\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]L=\\underset{n\\to \\infty }{\\text{lim}}{L}_{n}=\\infty[\/latex].<\/div>\n<p>&nbsp;<\/li>\n<li>Let [latex]{T}_{n}[\/latex] denote the area of each new triangle created when forming [latex]{F}_{n}[\/latex]. For [latex]n=0[\/latex], [latex]{T}_{0}[\/latex] is the area of the original equilateral triangle. Therefore, [latex]{T}_{0}={A}_{0}=\\frac{\\sqrt{3}}{4}[\/latex]. For [latex]n\\ge 1[\/latex], since the lengths of the sides of the new triangle are [latex]\\frac{1}{3}[\/latex] the length of the sides of [latex]{F}_{n - 1}[\/latex], we have<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169738080336\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{T}_{n}={\\left(\\frac{1}{3}\\right)}^{2}{T}_{n - 1}=\\frac{1}{9}\\cdot {T}_{n - 1}[\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nTherefore, [latex]{T}_{n}={\\left(\\frac{1}{9}\\right)}^{n}\\cdot \\frac{\\sqrt{3}}{4}[\/latex]. Since a new triangle is formed on each side of [latex]{F}_{n - 1}[\/latex], <span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169738088623\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]\\begin{array}{cc}\\hfill {A}_{n}& ={A}_{n - 1}+{N}_{n - 1}\\cdot {T}_{n}\\hfill \\\\ & ={A}_{n - 1}+\\left(3\\cdot {4}^{n - 1}\\right)\\cdot {\\left(\\frac{1}{9}\\right)}^{n}\\cdot \\frac{\\sqrt{3}}{4}\\hfill \\\\ & ={A}_{n - 1}+\\frac{3}{4}\\cdot {\\left(\\frac{4}{9}\\right)}^{n}\\cdot \\frac{\\sqrt{3}}{4}.\\hfill \\end{array}[\/latex]<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nWriting out the first few terms [latex]{A}_{0},{A}_{1},{A}_{2}[\/latex], we see that<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737269810\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]\\begin{array}{}\\\\ {A}_{0}=\\frac{\\sqrt{3}}{4}\\hfill \\\\ {A}_{1}={A}_{0}+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)\\cdot \\frac{\\sqrt{3}}{4}=\\frac{\\sqrt{3}}{4}+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)\\cdot \\frac{\\sqrt{3}}{4}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)\\right]\\hfill \\\\ {A}_{2}={A}_{1}+\\frac{3}{4}\\cdot {\\left(\\frac{4}{9}\\right)}^{2}\\cdot \\frac{\\sqrt{3}}{4}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)\\right]+\\frac{3}{4}\\cdot {\\left(\\frac{4}{9}\\right)}^{2}\\cdot \\frac{\\sqrt{3}}{4}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{3}{4}\\cdot \\left(\\frac{4}{9}\\right)+\\frac{3}{4}\\cdot {\\left(\\frac{4}{9}\\right)}^{2}\\right].\\hfill \\end{array}[\/latex]<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nMore generally,<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737226081\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{A}_{n}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{3}{4}\\left(\\frac{4}{9}+{\\left(\\frac{4}{9}\\right)}^{2}+\\cdots +{\\left(\\frac{4}{9}\\right)}^{n}\\right)\\right][\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nFactoring [latex]\\frac{4}{9}[\/latex] out of each term inside the inner parentheses, we rewrite our expression as<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737364353\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{A}_{n}=\\frac{\\sqrt{3}}{4}\\left[1+\\frac{1}{3}\\left(1+\\frac{4}{9}+{\\left(\\frac{4}{9}\\right)}^{2}+\\cdots +{\\left(\\frac{4}{9}\\right)}^{n - 1}\\right)\\right][\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nThe expression [latex]1+\\left(\\frac{4}{9}\\right)+{\\left(\\frac{4}{9}\\right)}^{2}+\\cdots +{\\left(\\frac{4}{9}\\right)}^{n - 1}[\/latex] is a geometric sum. As shown earlier, this sum satisfies<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737162064\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]1+\\frac{4}{9}+{\\left(\\frac{4}{9}\\right)}^{2}+\\cdots +{\\left(\\frac{4}{9}\\right)}^{n - 1}=\\frac{1-{\\left(\\frac{4}{9}\\right)}^{n}}{1-\\left(\\frac{4}{9}\\right)}[\/latex].<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nSubstituting this expression into the expression above and simplifying, we conclude that<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169738211851\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]\\begin{array}{cc}\\hfill {A}_{n}& =\\frac{\\sqrt{3}}{4}\\left[1+\\frac{1}{3}\\left(\\frac{1-{\\left(\\frac{4}{9}\\right)}^{n}}{1-\\left(\\frac{4}{9}\\right)}\\right)\\right]\\hfill \\\\ & =\\frac{\\sqrt{3}}{4}\\left[\\frac{8}{5}-\\frac{3}{5}{\\left(\\frac{4}{9}\\right)}^{n}\\right].\\hfill \\end{array}[\/latex]<\/div>\n<p><span data-type=\"newline\"><br \/>\n<\/span><br \/>\nTherefore, the area of Koch\u2019s snowflake is<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<div id=\"fs-id1169737201460\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]A=\\underset{n\\to \\infty }{\\text{lim}}{A}_{n}=\\frac{2\\sqrt{3}}{5}[\/latex].<\/div>\n<\/li>\n<\/ol>\n<\/div>\n<p>&nbsp;<\/p>\n<h3>Analysis<\/h3>\n<div id=\"fs-id1169738216901\" data-type=\"commentary\">\n<p id=\"fs-id1169738216906\">The Koch snowflake is interesting because it has finite area, yet infinite perimeter. Although at first this may seem impossible, recall that you have seen similar examples earlier in the text. For example, consider the region bounded by the curve [latex]y=\\frac{1}{{x}^{2}}[\/latex] and the [latex]x[\/latex] -axis on the interval [latex]\\left[1,\\infty \\right)[\/latex]. Since the improper integral<\/p>\n<div id=\"fs-id1169737910330\" class=\"unnumbered\" style=\"text-align: center;\" data-type=\"equation\" data-label=\"\">[latex]{\\displaystyle\\int }_{1}^{\\infty }\\frac{1}{{x}^{2}}dx[\/latex]<\/div>\n<p>&nbsp;<\/p>\n<p id=\"fs-id1169737910365\">converges, the area of this region is finite, even though the perimeter is infinite.<\/p>\n<\/div>\n<section id=\"fs-id1169737201473\" data-depth=\"1\">\n<h3 data-type=\"title\"><\/h3>\n<\/section>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-287\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Calculus Volume 2. <strong>Authored by<\/strong>: Gilbert Strang, Edwin (Jed) Herman. <strong>Provided by<\/strong>: OpenStax. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/openstax.org\/books\/calculus-volume-2\/pages\/1-introduction\">https:\/\/openstax.org\/books\/calculus-volume-2\/pages\/1-introduction<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA: Attribution-NonCommercial-ShareAlike<\/a><\/em>. <strong>License Terms<\/strong>: Access for free at https:\/\/openstax.org\/books\/calculus-volume-2\/pages\/1-introduction<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17533,"menu_order":28,"template":"","meta":{"_candela_citation":"{\"1\":{\"type\":\"cc\",\"description\":\"Calculus Volume 2\",\"author\":\"Gilbert Strang, Edwin (Jed) Herman\",\"organization\":\"OpenStax\",\"url\":\"https:\/\/openstax.org\/books\/calculus-volume-2\/pages\/1-introduction\",\"project\":\"\",\"license\":\"cc-by-nc-sa\",\"license_terms\":\"Access for free at https:\/\/openstax.org\/books\/calculus-volume-2\/pages\/1-introduction\"}}","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-287","chapter","type-chapter","status-publish","hentry"],"part":160,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/pressbooks\/v2\/chapters\/287","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/wp\/v2\/users\/17533"}],"version-history":[{"count":10,"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/pressbooks\/v2\/chapters\/287\/revisions"}],"predecessor-version":[{"id":1491,"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/pressbooks\/v2\/chapters\/287\/revisions\/1491"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/pressbooks\/v2\/parts\/160"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/pressbooks\/v2\/chapters\/287\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/wp\/v2\/media?parent=287"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/pressbooks\/v2\/chapter-type?post=287"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/wp\/v2\/contributor?post=287"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/calculus2\/wp-json\/wp\/v2\/license?post=287"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}