Question

In △ABC,a=34, b=18, and c=17. Find m∠A.

A. 14.1
B. 132.6
C. 152.5
D. 101.5

Answer 1

C.) 152.5

Explanation:

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Answer 2

C. m < A = 152.5 degrees.

Explanation:

Use the Cosine Rule:

a^2 = b^2 + c^2 - 2.b.c.cos A

34^2 = 18^2 + 17^2 - 2.18.17 cos A

2.18.17 cos A = 18^2 + 17^2 - 34^2

cos A = (18^2 + 17^2 - 34^2) / (2.18.17)

cos A = -0.88725

m < A = 152.5 degrees.