1.5 Measuring Angles Student Learning Goal: Students will measure angles and classify them by their size. Students will apply the Angle Addition Postulate.

1.5 Angle Measure Degree – A unit of measure used in measuring angles. 1° is 1/360 of an entire circle. An angle is formed by 2 noncollinear rays that have a common endpoint. The rays are called sides of the angle. The common endpoint is the vertex.

Example 1: Name all angles that have B as a vertex. Name the sides of 5. Write another name for 6. Example 4-1a

Classifying Angles • Right angle Acute angle m<A = 90° m<B is less than 90° Obtuse angle m<C is less than 180° & greater than 90°

Example 2: SIGNS A railroad crossing sign forms congruent angles. In the figure, WVX ZVY. If mWVX 7a + 13 and mZVY 10a – 20, find the actual measurements of WVX and ZVY. Example 4-3d

Example 3:

Angle Bisector A ray that divides an angle into two congruent angles is called an angle bisector.

𝑋𝑅 𝑏𝑖𝑠𝑒𝑐𝑡𝑠 ∡𝑊𝑋𝑍 𝑎𝑛𝑑 𝑋𝑆 𝑏𝑖𝑠𝑒𝑐𝑡𝑠 ∡𝑅𝑋𝑍. Example 4: 𝑋𝑅 𝑏𝑖𝑠𝑒𝑐𝑡𝑠 ∡𝑊𝑋𝑍 𝑎𝑛𝑑 𝑋𝑆 𝑏𝑖𝑠𝑒𝑐𝑡𝑠 ∡𝑅𝑋𝑍. 1.) Find h if m∡𝑅𝑋𝑆=5ℎ+3 𝑎𝑛𝑑 𝑚∡𝑆𝑋𝑍=2ℎ+6. 2.) Find b if ∡𝑊𝑋𝑅=2𝑏+1 𝑎𝑛𝑑 ∡𝑊𝑋𝑍=86°. Z R S W R X

HW pgs. 43-44 # 3, 4, 8, 9-14, 17-18, 21-30