## Key Concepts

**Supplementary and Complementary Angles**- If the sum of the measures of two angles is 180°, then the angles are supplementary.
- If angle [latex]A[/latex] and angle [latex]B[/latex] are supplementary, then [latex]m\angle{A}+m\angle{B}=180°[/latex] .
- If the sum of the measures of two angles is [latex]90^\circ[/latex], then the angles are complementary.
- If angle [latex]A[/latex] and angle [latex]B[/latex] are complementary, then [latex]m\angle{A}+m\angle{B}=90°[/latex] .

**Solve Geometry Applications**- Read the problem and make sure you understand all the words and ideas. Draw a figure and label it with the given information.
- Identify what you are looking for.
- Name what you are looking for and choose a variable to represent it.
- Translate into an equation by writing the appropriate formula or model for the situation. Substitute in the given information.
- Solve the equation using good algebra techniques.
- Check the answer in the problem and make sure it makes sense.
- Answer the question with a complete sentence.

**Sum of the Measures of the Angles of a Triangle**

- For any [latex]\Delta ABC[/latex], the sum of the measures is [latex]180^\circ[/latex]
- [latex]m\angle{A}+m\angle{B}=180°[/latex]

**Right Triangle**

- A right triangle is a triangle that has one [latex]90°[/latex] angle, which is often marked with a [latex]\angle[/latex] symbol.

**Properties of Similar Triangles**- If two triangles are similar, then their corresponding angle measures are equal and their corresponding side lengths have the same ratio.

## Glossary

**angle**- An angle is formed by two rays that share a common endpoint. Each ray is called a side of the angle.

**complementary angles**- If the sum of the measures of two angles is [latex]90^\circ [/latex] , then they are called complementary angles.

**hypotenuse**- The side of the triangle opposite the [latex]90^\circ[/latex] angle is called the hypotenuse.

**legs of a right triangle**- The sides of a right triangle adjacent to the right angle are called the legs.

**right triangle**- A right triangle is a triangle that has one [latex]90^\circ [/latex] angle.

**similar figures**- In geometry, if two figures have exactly the same shape but different sizes, we say they are similar figures.

**supplementary angles**- If the sum of the measures of two angles is [latex]180^\circ [/latex] , then they are called supplementary angles.

**triangle**- A triangle is a geometric figure with three sides and three angles.

**vertex of an angle**- When two rays meet to form an angle, the common endpoint is called the vertex of the angle.