cimag, cimagf,
  cimagl —
complex imaginary functions
#include <complex.h>
double
  
  cimag(double
    complex z);
float
  
  cimagf(float
    complex z);
long double
  
  cimagl(long
    double complex z);
These functions compute the imaginary part of z.
These functions return the imaginary part value (as a real).
For a variable z of complex type:
z = creal(z) + cimag(z)*I
 
Portions of this text are reprinted and reproduced in electronic form from IEEE
  Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
  Operating System Interface (POSIX), The Open Group Base Specifications Issue
  6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
  Engineers, Inc and The Open Group. In the event of any discrepancy between
  this version and the original IEEE and The Open Group Standard, the original
  IEEE and The Open Group Standard is the referee document. The original
  Standard can be obtained online at http://www.opengroup.org/unix/online.html .