Pi and the standard library

While I guess Pi is not explicitly shown in the math library, its trig functions work in radians and so the value of Pi is somewhat important to know. By playing with some of the trig functions, I found that the value it uses for Pi is one or two significant digits less than I expected, at least with my compiler. A trivial matter I suppose, but when my function figures out which side of a line a point is on, the answer might be different for certain situations if the value for Pi is different.

My question is this, "Will the different C/C++ compilers for the 32bit windows all use the same values for the standard library?" Or would I need to do some testing if I use diferent compilers?

Thanks in advance