www.LinuxHowtos.org

catan

Section: C Library Functions (3)
Updated: 202-0-08
Index Return to Main Contents

NAME

catan, catanf, catanl - complex arc tangents

LIBRARY

Math library (libm,~-lm)

SYNOPSIS

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

DESCRIPTION

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)

ATTRIBUTES

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

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

STANDARDS

C11, POSIX.-2008.

HISTORY

glibc 2.1. C99, POSIX.-2001.

EXAMPLES

/* 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>[rs]n", argv[0]);
        exit(EXIT_FAILURE);
    }
    z = atof(argv[1]) + atof(argv[2]) * I;
    c = catan(z);
    printf("catan() = %6.3f %6.3f*i[rs]n", creal(c), cimag(c));
    f = (clog(1 + i * z) - clog(1 - i * z)) / (2 * i);
    printf("formula = %6.3f %6.3f*i[rs]n", creal(f), cimag(f));
    exit(EXIT_SUCCESS); }