Commonly used standard math library functions

All functions return a double result and assume arguments are double x,y;
Include '#include ' at the top of the source file and link with '-lm' on the gcc command line.
On Linux type 'man function' to get a manual page on a given function.
sin of x with x in radians sin(x)
cosine of x with x in radians cos(x)
tangent of x with x in radians tan(x)
arctangent of x, returning 2 quadrant value in radians atan(x)
arctangent of y/x, returning 4 quadrant value in radians atan2(y,x)
e to the power x exp(x)
natural log of x log(x)
base 10 log of x log10(x)
hyperbolic sin of x sinh(x)
hyperbolic cosine of x cosh(x)
square root of x sqrt(x)
x to the power y pow(x,y)
absolute value of x fabs(x)