reverie414

I'm stuck with this 2 questions ... q1) Using laplace transforms, solve: y" + 4y = r(t), where r(t) = {3sint, 0<t<pi, -3sint, t>pi y(0)=0, y'(0)=3. this is what i get after rewriting for the step function: 3sint [1-u(t-pi)] + (-3sint)u(t-pi) ... im lost from then on. q2) Using the method of seperation of variables, solve the following partial differential equations: a)yux(subscript)-xuy(subscript)=0 b)ux(subscript)=yuy(subscript) i'm really at my wits end ... need to submit shortly afterwards. thanks a lot for the help.

Hi, I need urgent help with these 3 integrals problems ... been stuck on the questions and the deadline is Friday. Thanks a lot ! 1) For the green's theorem, I got the answer : 27.552. Not sure whether it is correct. Please kindly explain in steps so I know where I went wrong. 2) I'm totally unsure about finding the surface integral. How do I know the shape of the surface ? 3) and finding the curl function f All I know is, it has something to do with curl. Something like F = grad f. How do I find the function ? Thanks again !