What is x to the nearest tenth?
A.37.5
B.52.5
C.75.0
D.103.0
We can use the Law of Cosines here
31^2 = 39^2 + 22^2 - 2 (39 * 22) cos (ABC)
Rearrange as
cos (ABC) = [ 31^2 - 39^2 - 22^2 ] / [ -2 * 39 * 22 ] = 87 / 143
Taking the inverse cosine
arccos ( 87 / 143 ) ≈ 52.5° = x
