McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
3. Proving Triangles Congruent-SSS, SAS
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Exercise 40 Page 361

What do you know about angle measures in a triangle?

30

Practice makes perfect

We are given the measures of two angles in a triangle and are asked to find the measure of the third angle.

The Triangle Angle-Sum Theorem gives a relationship between these three angle measures. The sum of the interior angle measures in a triangle is180. We can use this relationship to find the measure of the angle at A.
m∠ R+m∠ S+m∠ A=180
41+ 109+m∠ A=180
Solve for m∠ A
150+m∠ A=180
m∠ A=30
The measure of the angle at A is 30.