Exercise 15 Page 116

We are given a triangle and asked to find the measure of the exterior angle.

To do so, let's recall the Exterior Angle Measures of a Triangle Theorem.

We will now identify the exterior angle and the two nonadjacent interior angles. Recall that the measure of a right angle is 90^(∘).

We can see that the measure of the exterior angle is x^(∘) and the measures of the nonadjacent interior angles are 38^(∘) and 90^(∘). By the Exterior Angle Measures of a Triangle Theorem, we can write an equation in terms of x. x^(∘)= 38^(∘)+ 90^(∘) Let's solve the equation! For simplicity, we will not write the degree symbol while solving.

The measure of the exterior angle is 128^(∘).