Question

How do I simplify `cosTheta(1+secTheta)(cosTheta-1)` ?

Answer 1

`costheta(1+ sectheta)(costheta-1)`

`=(costheta+ costheta*sectheta)(costheta-1)`

`=(costheta+ 1)(costheta-1)`

`=cos^2theta-1`

`=-sin^2theta`