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

If sec(theta+alpha)+sec(theta-alpha)=2sec theta, prove that cos theta=+-sqrt(2)(cos alpha)/(2)

If sec(theta+alpha)+sec(theta-alpha)=2sec theta and cos alpha!=1 , prove that cos theta=+-sqrt"cos"(alpha)/2

If sec(theta+alpha)+sec(theta-alpha)=2sec theta then show that cos^(2)theta=1+cos alpha

If sec(theta+alpha)+sec(theta-alpha)=2sec theta then show that cos^(2)theta=1+cos alpha

If sec(theta +alpha)+sec(theta-alpha = 2sectheta, costheta is equal to :

If sec(theta+alpha)+sec(theta-alpha)=2/costheta . then cos^2theta is equal to

If sec(phi+alpha)+sec(phi-alpha)=2sec phi, prove that cos phi=+-sqrt(2)(cos alpha)/(2)

If sec(x+alpha)+sec(x-alpha)=2sec x, prove that cos x=+-sqrt(2)cos((alpha)/(2))

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

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