Found interesting question on P3 mock paper that I'm not sure aout:-
Given that y=1 at x=pi, solve the differential equation:
dy/dx = y.x^2.cosx (y>0)
Any ideas? Never seen a question of this style before.
I thought that dy/dx had originated from 2 parametric equations (with t=parameter) and maybe dy/dt = y and dx/dt=secx/x^2?! Then thought about integrating them to get two equations?! Not sure though, any ideas!? Thanks! I'll probably end up posting a vector question as well tomorrow that I can't do, but I'm determined to work it out for myelf!
ln|y| = x^2.sinx - int (2x.sinx) dx = x^2.sinx - (2x(-cosx) - int (-2cosx))dx
ln|y| = x^2.sinx + 2x.cosx - 2sinx + C
Oooooh, so it's a question in the form:
dy/dx = f(x).g(x) which implies that:
integral 1/g(y).dy = integral f(x).dx + c
Silly me, I think I need to read through all of my notes again this weekend, before I try and do hard questions, esp those on paper we got for hw! What do I do then about the values of y and x it initially gives me? Do I put them into equation and solve to get a value of c?
Silly me, I think I need to read through all of my notes again this weekend, before I try and do hard questions, esp those on paper we got for hw! What do I do then about the values of y and x it initially gives me? Do I put them into equation and solve to get a value of c?