cos(theta)/(2)cos(theta)/(4)cos(theta)/(8)dots dots cos(theta)/(2^(n))

cos theta cos2 theta cos3 theta=(1)/(4)

Prove that: cos theta(cos theta)/(2)-cos3 theta(cos(9 theta))/(2)=sin7 theta s in8 theta

Solve cos2theta+cos8theta=cos5theta

1+cos2 theta+cos4 theta+cos6 theta=

cos 4theta = cos 3theta - cos2theta

4cos6 theta cos4 theta cos2 theta=

4 cos 6 theta cos 4 theta cos 2 theta =

(cos3 theta+2cos5 theta+cos7 theta)/(cos theta+2cos3 theta+cos5 theta)=cos2 theta-sin2 theta tan3 theta

If x = (1-cos^2 theta)/(cos theta), y = (1-cos^(2n)theta)/(cos^n theta) then show that (dy/dx)^2 = n^2((y^2 + 4)/(x^2 +4))