Usage and examples of the C library function asin()

C Standard Library <math.h>

The asin() function returns the arc sine value expressed in radians.

The asin() function takes a single parameter (1≥x≥-1），and returns the arc sine value in radians.

The asin() function is included in the <math.h> header file.

asin() prototype

double asin(double x);

要查找类型为int，float或long double的反正弦，可以使用强制转换运算符将类型显式转换为double。

　To find the arcsine of type int, float, or long double, you can use the explicit type conversion operator to convert the type to double.
　int x = 0;
　double result;

result = asin(double(x));99Additionally, C

float asinf(float x);
long double asinl(long double x);

asin() parameter

The asin() function uses-1,+1] range.1to-1between

asin() return value

The asin() function returns a double-precision value between-π/ 2,+π/ 2] returns this value in radians range. If the parameter passed to the asin() function is less than-1or greater1If the parameter of this function is less than or greater than the range, then the function returns NaN (Not a Number).

Example1: asin() function with different parameters

#include <stdio.h>
#include <math.h>
int main()
{
　　　　//　PI constant
　　　　const double PI =　　3.1415926;
　　　　double x, result;
　　　　x =　　-0.5;
　　　　result = asin(x);
　　　　printf("Inverse of sin(%.2f) arcsine value = %.2lf radians\n", x, result);
　　　　//Convert radians to degrees
　　　　result = asin(x)*180/PI;
　　　　printf("Inverse of sin(%.2f) arcsine value = %.2lf in degrees\n", x, result);
　　　　//Parameter is out of range
　　　　x =　1.2;
　　　　result = asin(x);
　　　　printf("Inverse of sin(%.2f) arcsine value = %.2lf, x, result);
　　　　return 0;
}

Output Result

sin(-0.50) arcsine value =　-0.52　Radians
sin(-0.50) arcsine value =　-30.00 degrees
sin(1.20) arcsine value = nan

Example2: asinf() and asinl() functions

#include <stdio.h>
#include <math.h>
int main()
{
　　　　float fx, fasinx;
　　　　long double lx, ldasinx;
　　　　//　floating-point arc sine
　　　　fx =　-0.505405;
　　　　fasinx = asinf(fx);
　　　　//　arcsine of long double type
　　　　lx =　-0.50540593;
　　　　ldasinx = asinf(lx);
　　　　printf("asinf(x) = %f radians\n", fasinx);
　　　　printf("asinl(x) Arcsine Value = %Lf Radians", ldasinx);
　　　　return 0;
}

Output Result

asinf(x) Arcsine Value =　-0.529851　Radians
asinl(x) Arcsine Value =　-0.529852　Radians

C Standard Library <math.h>