TAN(P) POSIX Programmer's Manual TAN(P)NAME
tan, tanf, tanl - tangent function
SYNOPSIS
#include <math.h>
double tan(double x);
float tanf(float x);
long double tanl(long double x);
DESCRIPTION
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 feclearexcept(FE_ALL_EXCEPT) before calling these
functions. On return, if errno is non-zero or fetestexcept(FE_INVALID
| FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
occurred.
RETURN VALUE
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 either 0.0 (if supported), or an imple‐
mentation-defined value shall be returned.
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 sup‐
ported), 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.
ERRORS
These functions shall fail if:
Domain Error
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.
Range Error
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:
Range Error
The result underflows, 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.
The following sections are informative.
EXAMPLES
Taking the Tangent of a 45-Degree Angle
#include <math.h>
...
double radians = 45.0 * M_PI / 180;
double result;
...
result = tan (radians);
APPLICATION USAGE
There are no known floating-point representations such that for a nor‐
mal argument, tan( x) is either overflow or underflow.
These functions may lose accuracy when their argument is near a multi‐
ple of pi/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.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOatan() , feclearexcept() , fetestexcept() , isnan() , the Base Defini‐
tions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
Conditions for Mathematical Functions, <math.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 TAN(P)
