McGraw Hill Glencoe Geometry, 2012
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McGraw Hill Glencoe Geometry, 2012 View details
4. Trigonometry
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Exercise 44 Page 575

You can use the sine ratio to find m ∠ K.

m ∠ J ≈ 69
m ∠ K ≈ 21
KL ≈ 20.5

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 ∠ J, m ∠ K, and KL.

Angle Measures

We can find m ∠ K using a sine ratio.
The sine of ∠ K is the ratio of the length of the leg opposite ∠ K to the length of the hypotenuse. sin K=opposite/hypotenuse ⇒ sin K =8/22 By the definition of the inverse sine, the inverse sine of 822 is the measure of ∠ K. To find it, we have to use a calculator.
m∠ K=sin ^(-1) 8/22
m∠ K = 21.32368...
m ∠ K ≈ 21
To find m∠ J, recall that the acute angles of a right triangle are complementary. Therefore, m ∠ J and m ∠ K add to 90. m ∠ J + m ∠ K = 90 Now, we can substitute the rounded measure of ∠ K in our equation and find the measure of ∠ J. m ∠ J + 21 = 90 ⇔ m ∠ J ≈ 69

Side Lengths

Finally, we can find the measure of KL. To do it, we can use the Pythagorean Theorem. (JL)^2 + (KL)^2 = (JK)^2 Let's substitute the known lengths, JL = 8 and JK= 22, into this equation to find KL.
(JL)^2 + (KL)^2 = (JK)^2
8^2+(KL)^2= 22^2
Solve for KL
64+(KL)^2=484
(KL)^2= 420
KL= sqrt(420)
KL =20.49390...
KL≈ 20.5