TAN(3) Library Functions Manual TAN(3)

tan — tangent function

#include <math.h>

double tan(double x);

The tan() function computes the tangent of its argument x , measured in radians.

An application wishing to check for error situations should set errno to 0 before calling tan(). If errno is non-zero on return, or the return value is NaN, an error has occurred.

The tan() function may lose accuracy when its argument is far from 0.0 .

Upon successful completion, tan() returns the tangent of x .

If x is NaN, NaN is returned and errno may be set to [EDOM].

If x is ±Inf, either 0.0 is returned and errno is set to [EDOM], or NaN is returned and errno may be set to [EDOM].

If the correct value would cause overflow, ±HUGE_VAL is returned and errno is set to [ERANGE].

If the correct value would cause underflow, 0.0 is returned and errno may be set to [ERANGE].

The tan() function will fail if:

The value to be returned would cause overflow.

The tan() function may fail if:

The value x is NaN or ±Inf.
The value to be returned would cause underflow.

No other errors will occur.

None.

None.

None.

atan(3) , isnan(3) , <math.h> .

Derived from Issue 1 of the SVID.

February 1997 posix.fail