A triangle has sides A, B, and C. Sides A and B are of lengths 9 and 7, respectively, and the angle between A and B is (7pi)/8 . What is the length of side C?

2 Answers
Nov 6, 2016

"C"=15.7

Explanation:

To answer this question, we have to use the law of cosines.

"C"^2="A"^2+"B"^2-2"AB"cos("c")=81+49-126cos(7/8pi) =246.4

"C"=sqrt264.4=15.7

Nov 6, 2016

2.0359.....

Explanation:

Cosine rule (rearranged for c) = c^2 = a^2+b^2-2ab*cosC

=c= sqrt(9^2+7^2-2*9*7*cos( (7pi)/8))

=2.035924013