About Function

I'm new to C in linux. Btw, I'm having a problem with function such as pow(x), sqrt(x), etc. For example, i wrote a program like this : #include #include main() { float a, b; b = pow(a, 3); printf("Result is : %f\n", b); } when i try to compile it using gcc, it keeps telling me an error like this ------> undefined 'pow' in main ....bla bla bla anyone can help?