Question

Given a triangle with a=80 b=51 and c=113, find C

Answer 1

use the Cosine Rule:-

c^2 = a^2 + b^2 - 2abcos C

113^2 = 80^2 + 51^2 - 2*80*51 cos C

cos C =  80^2 + 51^2 - 113^2
              --------------------------  =  -0.4617647
                     2 * 80 * 51

C =  117,5 degrees