If `3 tan theta tan phi=1`, then prove that 2 `cos (theta+varphi)=cos (theta-varphi)`.

If 3 tan theta tan phi=1 , then prove that 2 cos (theta+phi)=cos (theta-phi) .

If 3 tan theta tan phi=1, then (cos (theta-phi))/(cos (theta+phi)) is

If 3 tan theta tan phi=1, then (cos (theta-phi))/(cos (theta+phi)) is

If tan^2 theta = 1+2 tan^2 phi , prove that cos 2 phi = 1 + 2 cos 2 theta .

If t a n^2theta=2tan^2phi+1 , prove that cos2theta+sin^2phi=0.

If sin theta + cos theta =sqrt(3), then prove that tan theta + cot theta = 1 .

If tan theta tan phi=sqrt((a-b)/(a+b)) , prove that a-bcos 2theta)(a-b cos 2phi) is independent of theta and phi .

If sin2theta+sin2varphi=1/2a n d\ cos2theta+cos2varphi=3/2 , then cos^2(theta-varphi)= a. 3//8 b. 5//8 c. 3//4 d. 5//4

If 0 lt theta , phi lt pi and 8 cos theta cos phi cos (theta + phi)+1=0 find theta and phi

If tan^(4)theta +tan^(2) theta = 2 , then the value of cos^(4)theta +cos^(2)theta is-