Simplify and write the trigonometric expression in terms of sine and cosine:

http://webwork.mathstat.concordia.ca...4c19df41b1.png

http://webwork.mathstat.concordia.ca...14aa0b5111.png?

So I came up with this

http://webwork.mathstat.concordia.ca...485b290d01.png = 1/f(u)

But I am not sure what to do or if I am right?