asin

float       asinf( float arg );

double      asin( double arg );

long double asinl( long double arg );

#define asin( arg )

Parameters

Return value

If no errors occur, the arc sine of arg (arcsin(arg)) in the range [-

; +

], is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

If a range error occurs due to underflow, the correct result (after rounding) is returned.

Error handling

Errors are reported as specified in math_errhandling.

Domain error occurs if arg is outside the range [-1.0; 1.0].

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• If the argument is ±0, it is returned unmodified
• If |arg| > 1, a domain error occurs and NaN is returned.
• if the argument is NaN, NaN is returned

Example

#include <math.h>
#include <stdio.h>
#include <errno.h>
#include <fenv.h>
#include <string.h>
 
#pragma STDC FENV_ACCESS ON
int main(void)
{
    printf("asin( 1.0) = %+f, 2*asin( 1.0)=%+f\n", asin(1), 2*asin(1));
    printf("asin(-0.5) = %+f, 6*asin(-0.5)=%+f\n", asin(-0.5), 6*asin(-0.5));
    // special values
    printf("asin(0.0) = %1f, asin(-0.0)=%f\n", asin(+0.0), asin(-0.0));
    // error handling 
    errno = 0; feclearexcept(FE_ALL_EXCEPT);
    printf("asin(1.1) = %f\n", asin(1.1));
    if(errno == EDOM) perror("    errno == EDOM");
    if(fetestexcept(FE_INVALID)) puts("    FE_INVALID raised");
}

asin( 1.0) = +1.570796, 2*asin( 1.0)=+3.141593
asin(-0.5) = -0.523599, 6*asin(-0.5)=-3.141593
asin(0.0) = 0.000000, asin(-0.0)=-0.000000
asin(1.1) = nan
    errno == EDOM: Numerical argument out of domain
    FE_INVALID raised

References

• C11 standard (ISO/IEC 9899:2011):
  • 7.12.4.2 The asin functions (p: 238)
  • 7.25 Type-generic math <tgmath.h> (p: 373-375)
  • F.10.1.2 The asin functions (p: 518)
• C99 standard (ISO/IEC 9899:1999):
  • 7.12.4.2 The asin functions (p: 219)
  • 7.22 Type-generic math <tgmath.h> (p: 335-337)
  • F.9.1.2 The asin functions (p: 456)
• C89/C90 standard (ISO/IEC 9899:1990):
  • 4.5.2.2 The asin function

See also