McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
1. Angles of Triangles
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Exercise 14 Page 339

Look at the two triangles separately.

m∠ 1=m∠ 2=37.5^(∘)
m∠ 3=133^(∘)

Practice makes perfect

Consider the given triangles.

We want to find the measure of each numbered angle. Let's focus on triangles △ XYZ and △ XZW separately.

Finding m∠ 1 and m∠ 2

We will investigate △ XYZ first.
The markers at ∠ 1 and ∠ 2 indicate that these are congruent angles, so they have the same measure. m∠ 1=m∠ 2 We can use the given angle measure at X and the Triangle Angle-Sum Theorem to set up and solve an equation for m∠ 1. Recall that by this theorem, the sum of the measures of the three angles in a triangle is 180^(∘).
m∠ 1+m∠ 2+m∠ X=180 ^(∘)
m∠ 1+ m∠ 1+ 105 ^(∘)=180 ^(∘)
Solve for m∠ 1
2m∠ 1+105 ^(∘)=180 ^(∘)
2m∠ 1=75 ^(∘)
m∠ 1=37.5 ^(∘)
Since angles ∠ 1 and ∠ 2 are congruent, ∠ 2 has the same measure. m∠ 1=m∠ 2=37.5^(∘)

Finding m∠ 3

To find the measure of ∠ 3, let's shift our focus to triangle △ XZW. In this triangle, the measure of two angles are given and we are asked to find the measure of the third angle.

We can use the Triangle Angle-Sum Theorem again for △ XZW to set up and solve an equation for m∠ 3.
m∠ W+m∠ Z+m∠ 3=180 ^(∘)
23 ^(∘)+ 24 ^(∘)+m∠ 3=180 ^(∘)
Solve for m∠ 3
47 ^(∘)+m∠ 3=180 ^(∘)
m∠ 3=133 ^(∘)
The measure of ∠ 3 is 133^(∘).