Pearson Algebra 2 Common Core, 2011
PA
Pearson Algebra 2 Common Core, 2011 View details
3. Right Triangles and Trigonometric Ratios
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Exercise 54 Page 926

C

Practice makes perfect

We are given a right triangle ABC.

We are also given the following trigonometric expression. cos y^(∘) = 5/13 Recall that in a right triangle, the cosine of an acute angle is defined as the ratio of the adjacent side to the hypotenuse. cos θ = Adjacent/Hypotenuse We will compare the given expression with this definition. cos θ = Adjacent/Hypotenuse ⇒ cos y^(∘) = 5/13 Now, we can assume that the length of the adjacent side to y^(∘) is 5, and the length of the hypotenuse is 13.

Next, we will find the measure of x^(∘) by recalling the trigonometric ratio for sine. sin θ = Opposite/Hypotenuse Notice that this time, the side with length 5 is the opposite side to x^(∘) and the hypotenuse is 13.

We will rewrite the trigonometric ratio for sine by substituting these values. sin θ = Opposite/Hypotenuse ⇒ sin x^(∘) = 5/13 To obtain the measure of x^(∘), we will apply the inverse sine into each side of this equation. Let's do it!

sin x^(∘) = 5/13

sin^(-1)(LHS) = sin^(-1)(RHS)

x^(∘) = sin^(- 1) 5/13
x^(∘) = 22.619864 ...
x^(∘) ≈ 22.62 ^(∘)

Now, we want to find the value of z by using the following equation. x+2z = 7.1 To do so, we can substitute the value of x= 22.62 into this equation and solve it for z.

x +2z=7.1
22.62 +2z = 7.1
2z = - 15.52
z = - 7.76

Therefore, the correct answer is C.