" 30.If "tan(theta)/(2)=sqrt((1-e)/(1+e))tan(phi)/(2)," then the value of "cos phi" is: "

If tan[(theta)/(2)]=sqrt((1-e)/(1+e))tan[(phi)/(2)] then prove that cos phi=(cos theta-e)/(1-e cos theta)

If tan((pi)/(4)+phi)=(1)/(3) ,then the value of cos2 phi is

If tan""(theta)/(2)=sqrt((1-e)/(1+e))tan""(phi)/(2) . Then prove that cosphi=(costheta-e)/(1-ecostheta) .

If tan (theta/2) = sqrt((1-e)/(1+e)) tan(phi/2) ,then show that cos phi=(cos theta-e)/(1-ecos theta) .

If tan((theta)/(2))=5/2and tan((phi)/(2))=3/4, the value of cos(theta+phi), is

If tan((theta)/(2))=5/2and tan((phi)/(2))=3/4, the value of cos(theta+phi), is

If tan(theta)/(2)=sqrt((a-b)/(a+b))tan(phi)/(2), prove that cos theta=(a cos phi+b)/(a+b cos phi)

If tan theta = (1)/(2) and tan phi = (1)/(3) , then the value of theta + phi is