Question

lesson 2-3: exit ticket
what is m∠1?
what is m∠1?
60
70
120
130

Explanation:

Step1: Find m∠2

The exterior - angle of a triangle is equal to the sum of the two non - adjacent interior angles. The exterior angle at D is 130°, and the non - adjacent interior angles are ∠C and ∠2. So, ∠C+∠2 = 130°. Given ∠C = 70°, then ∠2=130° - 70° = 60°.

Step2: Find m∠1

Since ∠1 and ∠2 are a linear pair (they form a straight line), 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:

120