McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
6. The Law of Sines and Law of Cosines
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Exercise 40 Page 676

Begin by checking if the given triangle is a right triangle.

m ∠ K = 90
m ∠ J ≈ 59
m ∠ L ≈ 31

Practice makes perfect

Let's begin by drawing △ JKL and labeling the lengths of the sides. We will also color code the opposite angles and sides.

First, let's check whether the given triangle is a right triangle or not, by using Pythagorean Theorem. 56^2+ 33^2 = 65^2

The side lengths satisfy the Pythagorean Theorem. Therefore, we can conclude that the m∠ K will measure 90^(∘). Now, let's find the measures of ∠ J and ∠ L, one at a time.

Finding m ∠ J

Now that we know the given triangle is a right triangle, we can find m ∠ J by using the sine ratio. sin θ =opposite/hypotenuse Let's substitute the known side lengths to isolate sin J. sin J =opposite/hypotenuse ⇔ 56/65 Now we can use the inverse sine ratio to find m ∠ J.
m ∠ J = sin ^(-1) 56/65
m ∠ J ≈ 59.489762
m ∠ J ≈ 59

Finding m ∠ L

Finally, to find m ∠ L we can use the Triangle Angle Sum Theorem. This tells us that the measures of the angles in a triangle add up to 180. 90+ 59 + m ∠ L = 180 ⇔ m ∠ L ≈ 31

Completing the Triangle

With all of the angle measures, we can complete our diagram.