" 15.If "tan(theta)/(2)=sqrt((1-e)/(1+e))tan(varphi)/(2)," prove that "cos varphi=(cos theta-e)/(1-e cos theta)

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 (theta/2)=sqrt((1-e)/(1+e)) tan (varphi/2) ,then prove that cos varphi=(costheta-e)/(I-ecostheta)

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)=sqrt((1-e)/(1+e))tan(alpha)/(2), then cos alpha=1-e cos(cos theta+e)(b)(1+e cos theta)/(cos theta-e)(c)(1-e cos theta)/(cos theta-e) (d) (cos theta-e)/(1-e cos theta)

If tan((theta)/(2))=sqrt((1-e)/(1+e))tan((alpha)/(2)) then cos alpha=

If tan""((theta)/(2))=sqrt([(1-e)/(1+e)]) tan""((alpha)/(2)) then cos alpha=

If tan ((theta)/(2))= sqrt((1-e)/(1+e)) tan(( alpha)/(2)) then cos alpha=

If tan (phi /2)= sqrt((1+a)/(1-a)) tan"" theta/2," then prove that cos "phi=(cos theta-a)/(1-a cos theta)