Mathematica Help: Evaluating Expressions with Integers in Calculus

[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

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

 

[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.

 

[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.

 

[radou]

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

 

[Dragonfall]

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

 

[radou]

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.