I was doing my exam today and ran into a couple problems. First one: how do you differentiate [tex]\tan^2[/tex]? I converted it into [tex]\sec^2 - 1[/tex] and used the u/v = (u`v - v`u)/v^2 method, but I would like somebody clever to do it for me, just to be sure, please. 1. The problem statement, all variables and given/known data Another problem. Rate of change of population P equals [tex]\lambda P \cos(\lambda t)[/tex] Find the formula for population P in terms of [tex] P_0[/tex],[tex] \lambda[/tex] and t. Then, find t. When P = [tex]2P_0[/tex] 3. The attempt at a solution I had problems with finding t. t came out to be arcsin of something. The problem is, they never said anything about degrees or radians and so t could vary quite a bit, depending on that. Did I do it wrong or am I missing something out? I don't have the exact question. It was in the exam I did two hours ago. All help is appreciated. Thank you.