- #1
Gale
- 684
- 2
ok, i wasn't sure if i ought put this in math or phys, we're going over it my phys class, but its just math... whatever..
So i had to find the Fourier series representation of x^2 in the intervals (-pi, pi) and (0, 2pi). i haven't even started the (0, 2pi) one, cause i can't get the first half.
so i started with the coefficients, and for a_0 i got
[tex] a_0= 1/\pi \int_{-\pi}^\pi (0)^2 * cos(0*\pi) dx= 0[/tex] and i don't think that's right, the answer in the back of the book was... ok turns out i didn't write it down, but it was something + stuff*cos. So i assumed the something was the a_0/2 but i think it had pi^2 and i think it was over 3 or something, it seemed like maybe it wasn't a_0, so i kept going, with my a_n's.
so for a_n, i set it up, do integration by parts twice, and i get 0 again. same for b_n. i don't know what I'm doing wrong but everything keeps cancelling out and i get zeros. so could someone maybe help me through this problem? this isn't even an assigned problem, but i thought i'd try one i knew the answer to first, to make sure i knew what i was doing, but turns out i have no idea. help?
So i had to find the Fourier series representation of x^2 in the intervals (-pi, pi) and (0, 2pi). i haven't even started the (0, 2pi) one, cause i can't get the first half.
so i started with the coefficients, and for a_0 i got
[tex] a_0= 1/\pi \int_{-\pi}^\pi (0)^2 * cos(0*\pi) dx= 0[/tex] and i don't think that's right, the answer in the back of the book was... ok turns out i didn't write it down, but it was something + stuff*cos. So i assumed the something was the a_0/2 but i think it had pi^2 and i think it was over 3 or something, it seemed like maybe it wasn't a_0, so i kept going, with my a_n's.
so for a_n, i set it up, do integration by parts twice, and i get 0 again. same for b_n. i don't know what I'm doing wrong but everything keeps cancelling out and i get zeros. so could someone maybe help me through this problem? this isn't even an assigned problem, but i thought i'd try one i knew the answer to first, to make sure i knew what i was doing, but turns out i have no idea. help?
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