You did not take the derivative of the denominator while using Lhopital's rule!
Must have accidentally removed them while I was editing.. Anyway, thanks a lot for your help. I had one last question though.
Can you explain to me how he arrived at the firstequation from ?
I understand the second part, but the first part has me confused.
How did he get from ?
I understand the sin(2x) = 2sin(x)cos(x) part.