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In ΔJKL, j = 10 in., k = 7 in., and l = 6.58 in. Find m∠J.

A. 38º
B. 95º
C. 44º
D. 25º

1 Answer

5 votes

Answer:

B. 95°

Explanation:

Given the three sides of a triangle, the Law of Cosines can be used to find any of the angles.

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j² = k² +l² -2kl·cos(J) . . . . . law of cosines applied to this triangle

J = arccos((k² +l² -k²)/(2kl)) . . . . . solve for angle J

J = arccos((7² +6.58² -10²)/(2·7·6.58)) = arccos(-7.7036/92.12)

J ≈ 94.797° ≈ 95°

The measure of angle J is about 95°.
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Additional comment

Angle J is opposite side j, which is the longest side. That means angle J is the largest angle in the triangle. The largest angle of the triangle can never be less than 60°. Only one answer choice qualifies. (No computation is necessary.)

In ΔJKL, j = 10 in., k = 7 in., and l = 6.58 in. Find m∠J. A. 38º B. 95º C. 44º D-example-1
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