Ok, I'm making a program that does a lot of different kinds of math problems.

I have these as options:
1. Simple Operation (+,-,*,/)
2. Square roots
3. Powers
4. Areas
5. Volumes
6. Midpoint of a line
7. Slope of a line
8. Pythagorean theorem


What other types of math problems could I add to that? (about the same difficulty)