If `tan (theta/2) = sqrt((1-e)/(1+e)) tan(phi/2)`,then show that `cos phi=(cos theta-e)/(1-ecos theta)`.

Solve tan (2/3 theta)=sqrt(3)

If tan^2theta=1+2tan^2phi ,show that cos2phi=1+2cos2theta

If costheta+cos^2theta=1 ,show that 1/(cosec^2theta)+1/(cosec^4theta)=1

Solve the equation cos theta +cos 3 theta-2cos 2theta=0

Find cos^2 theta - sin^2 theta . .

If tan theta= (sqrt 2)-1 ,prove that sin theta cos theta = 1/2 . .

If sec theta=sqrt(2) and 3pi/2ltthetalt2pi ,find the value of (1+tan theta+cos theta)/(1+cot theta-cosec theta)

Express as product: cos2theta-cos8theta

Solve: 2cos^2theta-3costheta+1=0

If cos^2theta- sin^2theta= tan^2 phi , then prove that cos^2phi – sin^2phi= tan^2theta