(i) (1+sinθ)(1−sinθ)(1+cosθ)(1−cosθ)
=1−sin2θ1−cos2θ
=cos2θsin2θ=cot2θ=(78)2=4964
(ii) cotθ=78
tanθ=87
sec2θ=1+tan2θ
secθ=√1137
(1+sinθ)cosθ=1cosθ+sinθcosθ=secθ+tanθ=√1137+87=8+√1137
If cot θ=78, evaluate: (1+sinθ)(1−sinθ)(1+cosθ)(1−cosθ)