### Mathematical Functions for complex

The complex class defines a set of mathematical, trigonometric, magnitude, and conversion functions as friend functions of complex objects. They are:

> - exp (exponent)
> - log (natural logarithm)
> - pow (power)
> - sqrt (square root)
> - cos (cosine)
> - cosh (hyperbolic cosine)
> - sin (sine)
> - sinh (hyperbolic sine)
> - abs (absolute value or magnitude)
> - norm (square of magnitude)
> - arg (polar angle)
> - conj (conjugate)
> - polar (polar to complex)
> - real (real part)
> - imag (imaginary part)

Because these functions are friend functions rather than member functions, you cannot use the dot or arrow operators. For example:

complex a,b,*c;
a=exp(b); // correct - exp() is a friend function of complex
a=b.exp(); // error - exp() is not a member function of complex
a=c->exp(); // error - exp() is not a member function of complex