CATAN(3) Linux Programmer's Manual CATAN(3)

catan, catanf, catanl - complex arc tangents

#include <complex.h>
double complex catan(double complex z);
float complex catanf(float complex z);
long double complex catanl(long double complex z);
Link with -lm.

These functions calculate the complex arc tangent of z. If y = catan(z), then z = ctan(y). The real part of y is chosen in the interval [-pi/2,pi/2].
One has:
    catan(z) = (clog(1 + i * z) - clog(1 - i * z)) / (2 * i)

These functions first appeared in glibc in version 2.1.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
catan (), catanf (), catanl () Thread safety MT-Safe

C99, POSIX.1-2001, POSIX.1-2008.

/* Link with "-lm" */
#include <complex.h> #include <stdlib.h> #include <unistd.h> #include <stdio.h>
int main(int argc, char *argv[]) { double complex z, c, f; double complex i = I;
if (argc != 3) { fprintf(stderr, "Usage: %s <real> <imag>\n", argv[0]); exit(EXIT_FAILURE); }
z = atof(argv[1]) + atof(argv[2]) * I;
c = catan(z); printf("catan() = %6.3f %6.3f*i\n", creal(c), cimag(c));
f = (clog(1 + i * z) - clog(1 - i * z)) / (2 * i); printf("formula = %6.3f %6.3f*i\n", creal(f2), cimag(f2));

ccos(3), clog(3), ctan(3), complex(7)