Name
asin
Synopsis
Calculates the inverse sine of a number
#include <math.h> doubleasin
( doublex
); floatasinf
( floatx
); (C99) long doubleasinl
( long doublex
); (C99)
asin()
implements the
inverse sine function, commonly called arc
sine. The argument x
must be
between -1 and 1, inclusive: -1 ≤ x
≤ 1.
If x
is outside the function’s
domain—that is, if x
is greater than 1 or
less than −1—the function incurs a domain error.
The return value is given in radians, and is thus in the range
-π/2 ≤ asin(
x
)
≤ π/2.
Example
/*
* Calculate the altitude of the sun (its angle upward from the horizon)
* given the height of a vertical object and the length of the object's
* shadow.
*/
#define PI 3.141593
#define DEG_PER_RAD (180.0/PI)
float height = 2.20F;
float length = 1.23F;
float altitude =asinf
( height / sqrtf( height*height + length*length ));
printf( "The sun's altitude is %2.0f\xB0.\n", altitude * DEG_PER_RAD );
This code produces the following output:
The sun's altitude is 61°.
See Also
Arcsine functions for complex numbers: casin()
, casinf()
, and casinl()
Get C in a Nutshell now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.