cos `2theta cos 2phi + sin^(2) (theta - phi ) - sin^(2) ( theta + phi)` is equal to

Prove that cos 2 theta cos 2 phi + sin ^(2) ( theta - phi) -sin ^(2) (theta + phi) = cos ( 2 theta + 2 phi).

cos2thetacos2phi+sin^(2)(theta-phi)-sin^(2)(theta+phi) is equal to

cos2 theta cos2 phi+sin^(2)(theta-phi)-sin^(2)(theta+phi)=cos(2 theta+2 phi)

cos2thetacos2phi+sin^2(theta-phi)-sin^2(theta+phi)=

Prove that, cos^(2) (theta + phi) - sin^(2) (theta - phi) = cos 2 theta cos 2 phi

If x = cos theta cos phi + sin theta sin phi cos psi , y = cos theta sin phi - sin theta cos phi cos psi and z = sin theta sin psi , then x^(2) + y^(2) + z^(2) equals :

If cos theta+cos phi=a and sin theta - sin phi=b , then: 2cos(theta + phi) =

The value of ((sin theta + sin phi)/(cos theta + cos phi)+ (cos theta - cos phi)/(sin theta - sin phi)) is :