касательная функция (tangent function)
Пролог (Prolog)
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.
Имя (Name)
tan, tanf, tanl — tangent function
Синопсис (Synopsis)
#include <math.h>
double tan(double x);
float tanf(float x);
long double tanl(long double x);
Описание (Description)
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.1‐2017 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 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.
Возвращаемое значение (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 tan(), tanf(), and
tanl() shall return 0.0, or (if IEC 60559 Floating-Point is not
supported) an implementation-defined value no greater in
magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.
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 not returned, tan(), tanf(), and tanl() shall return an
implementation-defined value no greater in magnitude than
DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.
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.
Ошибки (Error)
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.
Примеры (Examples)
Taking the Tangent of a 45-Degree Angle
#include <math.h>
...
double radians = 45.0 * M_PI / 180;
double result;
...
result = tan (radians);
Использование в приложениях (Application usage)
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 π/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.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
atan(3p), feclearexcept(3p), fetestexcept(3p), isnan(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.20,
Treatment of Error Conditions for Mathematical Functions,
math.h(0p)
