## What you’ll learn to do: Calculate the arc length of a curve and the surface area of a solid of revolution

In this section, we use definite integrals to find the arc length of a curve. We can think of **arc length** as the distance you would travel if you were walking along the path of the curve. Many real-world applications involve arc length. If a rocket is launched along a parabolic path, we might want to know how far the rocket travels. Or, if a curve on a map represents a road, we might want to know how far we have to drive to reach our destination.

We begin by calculating the arc length of curves defined as functions of [latex]x,[/latex] then we examine the same process for curves defined as functions of [latex]y.[/latex] (The process is identical, with the roles of [latex]x[/latex] and [latex]y[/latex] reversed.) The techniques we use to find arc length can be extended to find the **surface area** of a surface of revolution, and we close the section with an examination of this concept.