Big Ideas Math: Modeling Real Life, Grade 8
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Big Ideas Math: Modeling Real Life, Grade 8 View details
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Exercise 7 Page 134

The measure of an exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent interior angles.

130^(∘)

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

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

Exterior Angle Measures of a Triangle Theorem

The measure of an exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent interior angles.

We will now identify the exterior angle and the two nonadjacent interior angles.

triangle

We can see that the measure of the exterior angle is j^(∘) and the measures of the nonadjacent interior angles are 90^(∘) and 40^(∘). By the Exterior Angle Measures of a Triangle Theorem, we can write an equation in terms of j. j^(∘)= 90^(∘)+ 40^(∘) Let's solve the equation! For simplicity, we will not write the degree symbol while solving. j=90+40 ⇔ j=130 The measure of the exterior angle is 130^(∘).