Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
2. Properties of Parallelograms
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Exercise 43 Page 374

Remember that opposite angles in a parallelogram are congruent by the Parallelogram Opposite Angles Theorem.

m∠ USV=16^(∘)

Practice makes perfect

We are given that in a parallelogram STUV, the measure of ∠ TSU is 32^(∘), the measure of ∠ USV is (x^2)^(∘), and ∠ TUV is an acute angle with a measure of 12x^(∘). Let's take a look at the given diagram.

Let's recall that opposite angles in a parallelogram are congruent by the Parallelogram Opposite Angles Theorem. Using this fact, we can write an equation for the given angle measures. m∠ TSU+m∠ USV=m∠ TUV 32^(∘)+ x^2^(∘)=12x^(∘)Now, we can solve the above quadratic equation for x. To do this, we will use the Quadratic Formula. ax^2+ bx+ c=0 ⇕ x=- b± sqrt(b^2-4 a c)/2 a Our first step will be to move all terms to one side of the equation. Then, we will identify the values of a, b, and c. 32+x^2=12x ⇕ 1x^2+( -12)x+ 32=0 We see that a= 1, b= -12, and c= 32. Let's substitute these values into the Quadratic Formula.
x=- b±sqrt(b^2-4ac)/2a
x=-( -12)±sqrt(( -12)^2-4( 1)( 32))/2( 1)
Solve for x and Simplify
x=12±sqrt((-12)^2-4(1)(32))/2(1)
x=12±sqrt(144-4(1)(32))/2(1)
x=12±sqrt(144-4(32))/2
x=12±sqrt(144-128)/2
x=12±sqrt(16)/2
x=12± 4/2
The solutions for this equation are x= 12± 42. Let's separate them into the positive and negative cases.
x=12± 4/2
x_1=12+4/2 x_2=12-4/2
x_1=16/2 x_2=8/2
x_1=8 x_2=4

Using the Quadratic Formula, we found that the solutions of the given equation are x_1=8 and x_2=4. Since we want ∠ TUV to be an acute angle, the value of 12x must be less than 90. Let's check for which solution this condition is satisfied. 12x_1=12(8)=96 * 12x_2=12(4)=48 ✓ Only when x=4 is ∠ TUV acute. Using this value, we can evaluate the exact measure of ∠ USV. m∠ USV=(x^2) ^(∘)=(4^2)^(∘)=16^(∘) The measure of ∠ USV is 16^(∘).