McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
5. Rhombi and Squares
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Exercise 11 Page 517

Consecutive angles in a parallelogram are supplementary.

m∠ DAB = 95

Practice makes perfect

Let's analyze the given rhombus.

To find the measure of the angle ∠ DAB, we first need to find the value of x. Recall that consecutive angles in a parallelogram are supplementary. This means that the measures of ∠ ABC and ∠ BCD add up to 180. m ∠ ABC+ m ∠ BCD = 180We are given that m ∠ ABC =2x-7 and m ∠ BCD = 2x+3. We can substitute these expressions into our equation. 2x-7+2x+3 = 180 Now we can solve this equation for x.
2x-7+2x+3 = 180
Solve for x
4x-4=180
4x=184
x=46
Notice that ∠ DAB is opposite to ∠ BCD. Since a rhombus is a parallelogram, its opposite angles are congruent. This means that their measures are equal. m ∠ DAB = m ∠ BCD We already know that m ∠ BCD =2x+3. Substituting this into the above equation, we get that m ∠ DAB= 2x+3 as well. Finally, we can substitute x=46 into this equation to find the measure of the angle.
m ∠ DAB = 2x+3
m ∠ DAB = 2( 46)+3
Evaluate right-hand side
m ∠ DAB = 92+3
m ∠ DAB = 95
We found that the measure of ∠ DAB is 95.