Answer: ∠1 = 90°
Explanation:
There are a few steps we will take to solve this problem. In each step, I will write an equation to help us solve, then use inverse operations to solve.
First, we will use the exterior angles theorem to find the measurement of ∠3 (this will help us solve for ∠2, then for ∠1).
89° = 51° + ∠3
∠3 = 38°
Next, we will find the measurement of ∠2 since we know ∠2 plus ∠3 is 90 degrees, as shown by the perpendicular lines and the box.
90° = ∠3 + ∠2
90° = 38° + ∠2
∠2 = 52°
Lastly, we will solve for ∠1. We know that there are 180 degrees in a triangle.
180° = 38° + ∠1 + ∠2
180° = 38° + ∠1 + 52°
180° = 90° + ∠1
∠1 = 90°