std::imag(std::complex)
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header <complex>
  | ||
| template< class T >  T imag( const complex<T>& z ); | ||
Returns the imaginary component of the complex number z, i.e. z.imag().
[edit] Parameters
| z | - | complex value | 
[edit] Return value
the imaginary component of z
[edit] See also
| accesses the real part of the complex number (public member function) | |
| accesses the imaginary part of the complex number (public member function) | |
|  imag | returns the imaginary component (function template) |