TAN(3) Library Functions Manual TAN(3)

tan tanf tanl — tangent function

#include <math.h>

double tan(double x);
float tanf(float x);
long double tanl(long double x);

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

These functions shall compute the tangent of their argument x, measured in radians.

An application wishing to check for error situations should set errno to zero and call (FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or (FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Upon successful completion, these functions shall return the tangent of x.

If the correct value would cause underflow, and is not representable, a range error may occur, and [MX] either 0.0 (if supported), or an implementation-defined value shall be returned.

[MX] If x is NaN, a NaN shall be returned.

If x is ±0, x shall be returned.

If x is subnormal, a range error may occur and x should be returned.

If x is ±Inf, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.

If the correct value would cause underflow, and is representable, a range error may occur and the correct value shall be returned.

If the correct value would cause overflow, a range error shall occur and tan (), tanf (), and tanl () shall return ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL, respectively, with the same sign as the correct value of the function.

These functions shall fail if:

[MX] The value of x is ±Inf.

If the integer expression ( math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [EDOM]. If the integer expression ( math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

[XSI] The result overflows

If the integer expression ( math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression ( math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.

These functions may fail if:

The result underflows, [MX] or the value of x is subnormal.

If the integer expression ( math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression ( math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

#include <math.h>
...
double radians = 45.0 * M_PI / 180;
double result;
...
result = tan (radians);

There are no known floating-point representations such that for a normal argument, tan ( x) is either overflow or underflow.

These functions may lose accuracy when their argument is near a multiple of /2 or is far from 0.0.

On error, the expressions ( math_errhandling & MATH_ERRNO) and ( math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

None.

None.

atan(3) , feclearexcept(3) , fetestexcept(3) , isnan(3)

XBD V1_chap04(7) , <math.h>

First released in Issue 1. Derived from Issue 1 of the SVID.

The last two paragraphs of the DESCRIPTION were included as APPLICATION USAGE notes in previous issues.

The tanf () and tanl () functions are added for alignment with the ISO/IEC 9899:1999 (“ISO C99”) standard.

The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 (“ISO C99”) standard.

IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 (“ISO C99”) standard are marked.

IEEE Std 1003.1-2001 (“POSIX.1”)/Cor 1-2002, item XSH/TC1/D6/64 is applied, correcting the last paragraph in the RETURN VALUE section.

January 1, 2008 posix.fail