Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
1. Angles of Triangles
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Exercise 18 Page 236

Consider the Exterior Angle Theorem.

68^(∘)

Practice makes perfect

Let's analyze the given triangle.

We can see that the measures of the interior angles are (x+8)^(∘) and 4x^(∘). According to the Exterior Angle Theorem, the measure of an exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent interior angles. This allows us to write an equation. 7x-16=(x+8)+4x We will now solve the above equation for x.
7x-16=x+8+4x
7x-16=5x+8
2x-16=8
2x=24
x=12
Now we can substitute x= 12 in the expression 7x-16 to find the measure of the angle. 7( 12)-16=68^(∘) Therefore, the measure of the exterior angle is 68^(∘).