(i)prove that 1/1+sintheta +1/1-sin theta=2sec^2 theta
(ii)prove that cos theta/1-sin theta =1+sin theta/cos theta
1 / ( 1 + sin theta ) + 1 / ( 1 - sin theta =
( 1 + sin theta + 1 - sin theta ) / [ ( 1 + sin theta ) * ( 1 - sin theta ) ] =
2 / ( 1 - sin ^ 2 theta ) =
2 / ( cos ^ 2 theta ) =
2 sec ^ 2 theta