Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
5. Measuring and Constructing Angles
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Exercise 27 Page 44

The sum of the unknown angles is 180^(∘).

m∠ LMP=77^(∘)
m∠ NMP=103^(∘)

Practice makes perfect

The expression m∠ LMP indicates the measure of the angle between two rays, ML and MP. Similarly, the expression m∠ NMP indicates the measure of the angle between rays MN and MP. To find their measures, let's start by identifying the three angles on a diagram.

Looking at the figures, and by the Angle Addition Postulate, we can see that m∠ LMN is equal to the sum of m∠ LMP and m∠ NMP. We can solve for x by creating an equation using the expressions for the two smaller angles and the value of the larger angle. Note that ∠ LMN is a straight angle, which is always equal to 180^(∘).
m∠ LMP+m∠ NMP=m∠ LMN
(- 16x+13)+(- 20x+23)=180
- 16x+13-20x+23=180
- 36x+36=180
- 36x=144
36x=- 144
x= - 4
Having solved the equation,we can calculate the individual angles by substituting x= - 4 into the expressions for the unknown angles. m∠ LMP &: - 16( - 4) +13 = 77^(∘) m∠ NMP &: - 20( - 4) +23 = 103^(∘)