Question

simplify: (csc^2(u) -1)sin^2(u)

Answer 1

change csc^2u into 1/sin^2u so that you have (1/sin^2u -1)sin^2u.
and then multiply the sin^2u outside the bracket with each term so that you are left with 1-sin^2u which is the same as cos^2u

Answer 2

thanks :)