This manual page is part of the POSIX Programmer’s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Name

Synopsis

Description

Return Value

Errors

Examples

Taking the Tangent of a 45-Degree Angle

Application Usage

Rationale

Future Directions

See Also

Copyright

tan, tanf, tanl - tangent function

#include <math.h>

double tan(doublex);

float tanf(floatx);

long double tanl(long doublex);

These functions shall compute the tangent of their argument

x, measured in radians.An application wishing to check for error situations should set

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(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 either 0.0 (if supported), or an implementation-defined value shall be returned.

If

xis NaN, a NaN shall be returned.If

xis ±0,xshall be returned.If

xis subnormal, a range error may occur andxshould be returned.If

xis ±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(), andtanl() 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:

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

Domain Error The value of xis ±Inf.If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errnoshall 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 errnoshall 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 xis subnormal.errnoshall 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.

#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 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.

None.

None.

atan() ,feclearexcept() ,fetestexcept() ,isnan() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions,<math.h>

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 |
TAN (P) | 2003 |