Mathematica Help

1. Oct 29, 2006

Dragonfall

I want mathematica to evaluate a certain expression (see attached) assuming that n is an integer. The answer is far from what it produces. Maple produces the right answer but I don't have access to it.

The expression is

$$\frac{\int_{-\pi}^{\pi}|\sin(x)|\cos(nx)\dx}{\int_{-\pi}^{\pi}\cos^2(nx)\dx}$$

Attached Files:

• Picture 1.png
File size:
1.3 KB
Views:
86
Last edited: Oct 29, 2006
2. Oct 30, 2006

Stephan Hoyer

You need to put a space between your n and x. Mathematica is treating nx as a single variable, which explains the funky result.

3. Oct 30, 2006

FredGarvin

One other thing to try...I don't have Mathematica in front of me here at work, but I do remember also reading an article about Mathematica getting into a bit of trouble in some cases when using the sybolic integration sign. If Stephan's tip doesn't help, you may try using "Integrate" instead of the symbolic operator.

4. Oct 30, 2006

Use '*' everywhere, to avoid possible problems. Doesn't look nice, though, but nevermind.

5. Oct 30, 2006

Dragonfall

The error was the missing *. Thanks for the help.

6. Oct 30, 2006

Yes. But note that, as someone above stated, you can simply use the space bar instead of '*'. Mathematica will produce a small space between the two object that are multiplied.