# Mathematica Help

• Mathematica
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

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

#### Attachments

• Picture 1.png
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## Answers and Replies

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

FredGarvin
Science Advisor
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.

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

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

radou
Homework Helper
Dragonfall said:
The error was the missing *. Thanks for the help.

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.