# Calculators Fourier and TI-89

1. Dec 9, 2004

### TSN79

I'm currently working with Fourier-series and have to integrate some expressions, like this one:

$$2\int_{0}^{1} (1-x)*sin(n \omega x) dx = 2 \left[- \frac{1}{n \pi}(1-x) cos(n \pi x) - \frac{1}{(n \pi)^2} sin(n \pi x) \right]_{0}^{1} = \frac{2}{n \pi}$$

Trying to evaluate this (with $$\omega = \pi$$)on the TI-89 does not give this result. And the thing is that if I remove the n from the sine and cosine expressions, then the answer comes out right. Why is this? Should I assume the n is 1 in the sine and cosine functions in the square parentheses?

2. Dec 9, 2004

### fourier jr

i don't think i've used one of those calculators before but maybe it doesn't know what n is. (real, complex, integer, a variable like x, y, z, etc etc) i don't think maple always knows either. sometimes it gives the most general answer possible & i have to tell it to give me a positive integer, or it just spits out the same thing i typed in because i wasn't specific enough with what i wanted it to do.