Given Sinu= -5/13 and pi< u <3pi/2 Find each of the following: A.Cos2u= B. Cos u/2=

Answer 1

cos u = -12/13 (because you are dealing with a 5, 12, 13 right triangle.

cos 2u = cos²u - sin²u

cos (u/2) = sqrt[(1+cos u )/2]