In triangle ABC, side AB = 10, side AC = 13, and side BC = 16. What is the measure of the larges angle in degrees?

Question

In triangle ABC, side AB = 10, side AC = 13, and side BC = 16.  What is the measure of the larges angle in degrees?

Reiny · Answer

the larger angle Ø must be across from the larger side, so by the cosine law.... 16^2 = 10^2+13^2 - 2(10)(13)cosØ 260cosØ = 13 cosØ = 13/260 = 1/20 = .05 Ø = 87.1°