hey so i'm helping a friend with a c++ program. the program has to determine thrust and torque of a propeller blade. in order to get those values u have to use integral math equations. how do u do those in c++? is there an open source class i can find that will let me do it? i am totally lost on how do this portion. i've already tried cmath. help!

Wow. You want a library that can parse hand-typed math equations, solve them, and perform calculus on them? That's a tall order; I doubt there's anything like that for free, though if there is, your best bet is to look on SourceForge. Good luck getting your prof to approve of using someone else's code. Wouldn't it just be easier to take the formula to calculate thrust, derive it by hand to find the fomula for torque, and hard-code the derivative into the program? Or, if you don't know the formula for thrust, then you could integrate the torque formula by hand instead. What you're asking for is a language interpreter (like the Java Virtual Machine, for example); it has to be easier to halfass it and still get a decent grade. I doubt the prof even knows calculus, anyway.

you know the equations youre going to use right? the user would just have to enter certain coefficients or other constants for certain cases?

I googled integrals in C++ and got some responses that might help. This one does an integral for the sin function but it requires you to register to get access to the library. You will prolly need to d/l a library to handle this then just include it in your program. I'll let you look for all that tho http://www.codecogs.com/d-ox/maths/special/sine_power_integral.php This next link is a book you might be interested in. http://www.cambridge.org/uk/catalogue/catalogue.asp?isbn=0521750334 Sorry...to tired to search anymore.

GNU Octave? Not a C++ library but you should still be able to use it (and maybe there's a library interface). I'm not sure if it can do what you need though... This might be handy: http://orms.mfo.de/show.php?query_mode=classif&classif=05&descr=Differential%20and%20Integral%20Equations