Question

Given: ΔABC; a= 10; b = 4, and c = 11. Find the measurement of ∠B to the nearest tenth of a degree.

Answer 1

Use the Cosine Rule to find this

cos <B  = [b^2 - a^2 - c^2] /  -2ac 

               =  [ 4^2 - 10^2 - 11^2] / -2*10*11

               =   0.93182

so m < B  =   21.3 degrees to nearest tenth.  Answer