#include <math.h> double tan(double x); float tanf(float x); long double tanl(long double x);
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.
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.
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.
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:
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.
#include <math.h> ... double radians = 45.0 * M_PI / 180; double result; ... result = tan (radians);
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.
The Base Definitions volume of POSIX.1-2017, Section 4.20, Treatment of Error Conditions for Mathematical Functions, <math.h>
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