Question

How do you multiply and simplify `(tany-coty)(tany+coty)`?

Answer 1

`(tany-coty)(tany+coty) -= tan^2y-cot^2y`

Explanation:

We have an expression,

`E = (tany-coty)(tany+coty)`

This is the difference of two squares, thus we can write:

`E = tan^2y-cot^2y`

The issue of "simplify" is somewhat ambiguous - there are many other ways we can write the expression!