If `cos(theta - alpha) , costheta , cos(theta + alpha)` are in H.P. then `costheta.sec(alpha/2) = `

If cos(theta-alpha),cos(theta),cos(theta+alpha) are in H.P. then costheta.secalpha/2

If cos(theta-alpha),costheta,cos(theta+alpha) are in H.P.,then costhetasec(alpha//2) is equal to

If cos (theta - alpha),cos(theta),Cos(theta + alpha) are in H.P. and cos alpha ne 1 , then angle alpha lie in the

cos2 theta+2 costheta is always

If cos^4 theta sec^2 alpha,1/2 and sin^4 theta cosec^2 alpha are in A.P. , then cos^8 theta sec^6 alpha ,1/2 and sin^8 theta cosec^6 alpha are

Simplify be reducing to a single term : cos (theta + alpha ) cos ( theta - alpha ) - sin ( theta + alpha ) sin (theta - alpha).

Show that the lines (1-cos theta tan alpha) y^2 -(2cos theta+sin ^2 theta tan alpha )xy +cos theta (cos theta+tan alpha )x^2=0 include an angle alpha between them .

If sin (theta + alpha ) = cos ( theta + alpha), prove that tan theta =(1- tan alpha )/(1 + tan alpha )

If sec(theta+alpha)+sec(theta-alpha)=2\ s e ctheta, prove that costheta=+-sqrt(2)cosalpha/2dot

Prove that cos 4theta–cos 4alpha = 8(cos theta-cos alpha)(cos theta+ cos alpha )(cos theta -sin alpha)(cos theta+sin alpha)