Hi... I was just wondering if anyone could give me a hand with this problem. It's probably pretty simple but I can't seem to see the progression between the two lines... I'm guessing there's some use of trig identity cos^2t + sin^2t = 1... If anyone could break it down a bit further it would be much appreciated:

= -2sin^2t - cos^2t .dt

* * *

= (-1 - sin^2t).dt