Question

what is m∠1? o a 130 o b 70 o c 60 o d 120

Explanation:

Step1: Find angle 2

The exterior - angle of a triangle is equal to the sum of the two non - adjacent interior angles. At point D, the exterior angle is 130°. Let the non - adjacent interior angles be ∠C = 70° and ∠2. So, ∠2+70° = 130°. Then ∠2=130° - 70° = 60°.

Step2: Find angle 1

Since ∠1 and ∠2 are supplementary (they form a linear pair), and the sum of angles in a linear pair is 180°. So, ∠1+∠2 = 180°. Substitute ∠2 = 60° into the equation: ∠1=180° - 60° = 120°.

Answer:

D. 120