TAN

PROLOG

NAME

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 implementation-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 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.  

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 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.  

RATIONALE

None.  

FUTURE DIRECTIONS

None.  

SEE ALSO

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>  

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