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

(sin (theta + phi))/( sin theta cos phi) = cot theta tan phi +1.

If cos(theta+phi)= mcos(theta-phi) , then prove that tan theta=(1-m)/(1+m)cotphi .

If sin theta is G.M. of sin phi and cos phi, then prove that cos 2 theta = 2 cos ^(2) ((pi)/(4) + phi).

If cos(theta-phi) , cos(theta) , cos(theta+phi) are in HP, the the value of cos(theta)sec(phi/2) is

Prove: (sin phi - cos phi) ^(2) =1 - sin 2 phi.

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

tan 4 phi in terms of cos 8phi,

If 3(cos 2phi-cos2theta)=1-cos2phi cos2theta , then tan theta= k tan phi , where theta, phiin (0,(pi)/(2)) , where k =

Suppose theta and phi(ne 0) are such that sec (theta+phi), sec theta and sec (theta-phi) are in A.P. If cos theta=kcos((phi)/(2)) for some k, then k is equal to

Show that (1+tan .theta/2)/(1-tan. theta/2)=(1+sintheta)/(cos theta)=tan(pi/4+theta/2)