1. Geometry 1-3 Angle Addition Angle Addition Postulate: If a ray cuts an angle into two or more parts, the sum of the parts equals the whole angle. part 1 + part 2 = the whole R Q S P

2. Example If Y is in the interior of LMN, find the m LMY if m LMY = 5x+3, m YMN = 3x+3, and m LMN=86°. LMY + YMN = LMN (5x + 3) + (3x + 3) = 86 8x + 6 = 86 8x = 80 x = 10 m LMY = 5(10) + 3 = 53 L M N Y

3. Example MX bisects LMN. If m LMX = 3x and m NMX = 5x – 20, what is m LMN? LMX = NMX 3x = 5x – 20 -2x = -20 x = 10 m LMN = 3(10) + 5(10) – 20 = 60 L M N X