Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
6. Describing Pairs of Angles
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Exercise 35 Page 53

The angles in a linear pair are supplementary angles.

Algebraic Equation: x+(2/3x-15)=180
Measures of the Angles: 117^(∘) and 63^(∘)

Practice makes perfect
Let's call the unknown angles ∠ A and ∠ B. We know that ∠ A and ∠ B form a linear pair, and, therefore, they are supplementary angles. Since the sum of measures of supplementary angles is 180^(∘), we can write an equation. m∠ A + m∠ B = 180^(∘) We are told that the measure of one angle is 15^(∘) less than 23 the measure of the other angle. Assume that the measure of ∠ A is x. We then have the following expressions for the measures of the unknown angles. m∠ A =& x [0.5em] m∠ B =& 2/3x- 15 Substituting these values into the sum gives us the desired algebraic equation. m∠ A+ m∠ B&=180 x+ (2/3x-15)&=180 Now we can solve for x and find the measures of the angles.
x+(2/3x-15)=180
x+2/3x-15=180
1 23x-15=180
1 23x=195
Write mixed number as a fraction
3+2/3x=195
5/3x=195
5x=585
x=117
Knowing that x=117^(∘), we can determine the measures of the angles. &m∠ A ⇒ x= 117^(∘) [0.5em] &m∠ B ⇒ 2/3x-15= 2/3( 117)-15=63^(∘)