McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
4. Rectangles
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Exercise 16 Page 508

Notice that ∠ ZYW and ∠ WYX are complementary angles.

m ∠ ZYW = 39

Practice makes perfect

Let's analyze the given quadrilateral so that we can find the measure of ∠ ZYW.

First, we must find the value of x. By the definition of a rectangle, we know that WXYZ has four right angles. Therefore, the measure of m ∠ XYZ is 90. m ∠ XYZ= 90 With the Angle Addition Postulate we can express m ∠ XYZ as a sum of m ∠ ZYW and m ∠ WYX. Since ∠ XYZ is a right angle and its measure is 90, this means that ∠ ZYW and ∠ WYX are complementary angles. m ∠ ZYW + m ∠ WYX = m ∠ XYZ ⇕ m ∠ ZYW + m ∠ WYX = 90 We are given that m ∠ ZYW= 2x-7 and m ∠ WYX= 2x+5. We will substitute these expressions into our equation. 2x-7 + 2x+5 = 90 Let's solve it!
2x-7 + 2x+5 = 90
Solve for x
4x-2=90
4x=92
x=23
Finally, we can substitute x=23 back into the expression for m∠ ZYW to find the measure of the angle.
m ∠ ZYW =2x-7
m ∠ ZYW =2( 23)-7
m ∠ ZYW = 46 - 7
m ∠ ZYW = 39