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

Answer:

C.  m < A = 152.5 degrees.

Step-by-step 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.