Cos2x=2(cosx)^2-1 therfor
(cosx)^2=(1+cos2x)/2
as
(1/2)[cos^2(x)] +C=(1/4)[cos2(x)]
1/2((1+cos2x)/2)+C=(1/4)[cos2(x)]
1/2+(cos2x)/4+C=(1/4)[cos2(x)] Mr F says: That red 2 should be a 4.
1/2+C=0
C=-1/2
Actually C = -1/4.
You should have tested it using a simple value of x lol!!