Originally Posted by

**Paymemoney** Hi

I have a few questions in can't get the right answers:

1)Simply the expression $\displaystyle sin^4x-cos^4x$ Note that this is the difference of squares.

2)Simply the expression $\displaystyle tan^3x+tanx$ Factor out a tanx, then note that (tan^2x+1)=sec^2x. What you have done is unneccesary.

This is what i have done:

=$\displaystyle \frac{sinx^3}{cosx^3}+\frac{sinx}{cosx}$

=$\displaystyle \frac{sinx^3}{cos^3}+\frac{sinxcosx^2}{cosx^3}$

what should i do next?

3)if tanx=-4,x [$\displaystyle \frac{-\pi}{2},0$] find: sec(x)

P.S