catan(3) Library Functions Manual catan(3)

catan, catanf, catanl - complex arc tangents

Math library (libm, -lm)

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

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)

For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
catan (), catanf (), catanl () Thread safety MT-Safe

C11, POSIX.1-2008.

glibc 2.1. C99, POSIX.1-2001.

/* Link with "-lm" */
#include <complex.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.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(f), cimag(f));
    exit(EXIT_SUCCESS);
}

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

2024-05-02 Linux man-pages 6.8