McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
4. Rectangles
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Exercise 6 Page 508

Since the given quadrilateral is a rectangle, it has four right angles.

51

Practice makes perfect

Let's analyze the given rectangle so that we can find m∠ EFD.

By the definition of a rectangle, we know that DEFG has four right angles. Therefore, the measure of m ∠ EFG is 90. m ∠ EFG= 90 With the Angle Addition Postulate we can express m ∠ EFG as a sum of m ∠ EFD and m ∠ DFG. m ∠ EFD + m ∠ DFG = m ∠ EFG ⇕ m ∠ EFD + m ∠ DFG = 90 We are given that m ∠ EFD= 2x-3 and m ∠ DFG= x+12, and we have been asked to find the measure of ∠ EFD. We will first substitute these expressions into our equation for m∠ EFG to find the value of x. Then we can substitute the value of x into the equation of m∠ EFD to find its measure. 2x-3 + x+12 = 90 Let's solve it!
2x-3 + x+12 = 90
Solve for x
3x+9=90
3x=81
x=27
Now, we can substitute x=27 into the equation of m∠ EFD and find the measure of the angle.
m ∠ EFD = 2x-3
m ∠ EFD = 2( 27) -3
m∠ EFD = 54-3
m ∠ EFD = 51