Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
6. Solving Right Triangles
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Exercise 17 Page 505

Find the measure of ∠ K first. Then, you can use the sine ratio to find ML and cosine ratio to find KL.

m ∠ K = 50
ML ≈ 6.1
KL ≈ 5.1

Practice makes perfect

Let's analyze the given right triangle.

We will find the missing measures one at a time. In this case, this means that we want to find m ∠ K, ML, and KL.

Angle Measures

To find m∠ K, recall that the acute angles of a right triangle are complementary. Therefore, m ∠ K and m ∠ M add to 90.

m ∠ K + m ∠ M = 90 Since we know the measure of ∠ M, we can substitute it in our equation and find the measure of ∠ K. m ∠ K + 40 = 90 ⇔ m ∠ K = 50

Side Lengths

We can find the measure of ML and KL using sine and cosine ratios respectively.

The sine of ∠ K is the ratio of the length of the leg opposite ∠ K to the length of the hypotenuse. Sine=Opposite/Hypotenuse ⇒ sin 50^(∘) =x/8 We can use the obtained equation to find the measure of ML. We have to use the calculator to find the value of the given sine. Then, we will substitute it into the equation and solve for x.
sin 50^(∘)=x/8
0.766044 = x/8
Solve for x
6.128352=x
x=6.128352
x ≈ 6.1
Therefore, the measure of ML is 6.1, rounded to nearest tenth. The cosine of ∠ K is the ratio of the length of the adjacent leg of ∠ K to the length of the hypotenuse. Cosine=Adjacent/Hypotenuse ⇒ cos 50^(∘) =y/8 We can use the obtained equation to find the measure of KL. We have to use the calculator to find the value of the given cosine. Then, we will substitute it into the equation and solve for y.
cos 50^(∘)=y/8
0.642788 = y/8
Solve for y
5.142304=y
y=5.142304
y ≈ 5.1
Therefore, the measure of KL, rounded to nearest tenth, is 5.1.