Hi there. I have some trouble with this problem, it asks me to find the fourier expansion series for the function

So I've found the coefficients

Then the fourier series expansion:

When I plot this on mathematica I get something that doesn't look like what I'm looking for. I've tried many ways, I've done the integrals first by hand, then I did it with mathematica, the graph always seems the same, it doesn't get to zero in the interval zero to -pi as it should, and it isn't close to the plot of t^2, it doesn't even get to zero on the origin. I don't know what I'm doing wrong. I've looked at the equations carefully, I'm pretty much sure I've done things right. Whats happening?

I've also tried to make a distinction between the odd and even cases, but as I supposed it didn't affect at all, the equation as I wrote it includes both cases.