Eliminate `theta " and " phi`
`tan theta + tan phi = x, cot theta + cot phi = y, theta + phi = alpha`

Eliminate theta " and " phi sin theta + sin phi = a, cos theta + cos phi = b, 0 - phi = alpha

If (1 + tan theta) (1+ tan phi) = 2, then theta + phi =

If tan theta+tan phi=a and cot theta+cot phi=b then cot(theta+phi)=

If tan theta + tan phi =a , and cot theta + cot phi =b , and theta - phi = alpha ne 0 , then

tan theta+tan phi=a,cot theta+cot phi=b,theta-phi=alpha!=0

Eliminate theta, phi from sin theta + sin phi = a , cos theta+ cos phi = b and tan theta/2 * tan phi/2 = c.

Eliminate theta and phi sintheta+sinphi=a , costheta+cosphi=b , theta-phi =a

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