(cosA)^2=( 1+cos2A)/2

(sinA)^2=( 1-cos2A)/2

(tana) 2 = (1-cos (2α))/(1+cos (2α)) The formula is as follows.

The direct application of the double-angle formula is to raise the power, and the formula Cos2α can be deformed to get the formula of decreasing the power:

cos2α=(cosα)^2-(sinα)^2=2(cosα)^2- 1= 1-2(sinα)^2

cos2α=2(cosα)^2- 1,(cosα)^2=(cos2α+ 1)/2

cos2α= 1-2(sinα)^2,(sinα)^2=( 1-cos2α)/2