Hey,

How would I specify an interval for a function?
Is an if absolutely needed?

Example:
solve(cos(x)=0, x)

I would like an answer between 0 and 2*PI.

In my calculator, it can be accomplished as such:
solve(cos(x)=0, x {0, 2*PI}) = 1.57...

The range is specified as the third and fourth argument.
solve(cos(x)≡0;x;0;2*π)=mat(1,5708;4,7124;2;1)
(Pay attention on Boolean equal to, and function argument separator - here at the forum we must us ";" with MATH tag, but you can use either ";" or "," depending on regional settings)
If you do not specify the root find range, it is defined by default in Tools=>Options=>Roots(range). If you keep say the range [-100,100], with solve(cos(x)=0, x)= you will have lots of roots there.

Regards,
Radovan

EDIT: BTW, you can visit this wiki page

Edited by user 27 October 2009 22:04:10(UTC)  | Reason: Not specified