Exercise 3 Page 113

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.

We can see that the measure of the exterior angle is y^(∘) and the measures of the nonadjacent interior angles are 40^(∘) and 30^(∘). By the Exterior Angle Measures of a Triangle Theorem, we can write an equation in terms of y. y^(∘)= 40^(∘)+ 30^(∘) Let's solve the equation! For simplicity, we will not write the degree symbol while solving.

The measure of the exterior angle is 70^(∘).