CLOG(3) | Library Functions Manual | CLOG(3)

# NAME

`clog`, `clogf`, `clogl` — complex natural logarithm

# SYNOPSIS

Math Library (libm, -lm)
`#include <complex.h>`

double complex
`clog`(double complex z);

float complex
`clogf`(float complex z);

long double complex
`clogl`(long double complex z);

# DESCRIPTION

The `clog`(), `clogf`() and `clogl`() functions compute the complex logarithm to the base e (2.718...) of z.

If z = x + iy, then

    clog(z) = log(sqrt(x^2 + y^2)) + i atan(y / x).

# RETURN VALUES

The `clog`(), `clogf`() and `clogl`() functions return the complex logarithm to the base e of z with imaginary part in the interval [-Pi, Pi], and unbounded real part.

# SEE ALSO

cexp(3), cpow(3)

# STANDARDS

The `clog`(), `clogf`() and `clogl`() functions conform to ISO/IEC 9899:1999 (“ISO C99”).

June 7, 2025 | Debian