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asin - Returns sine value in C

The asin function computes the principal value of the arc sine of x in the range [-1,1], returning a value in the interval [-pi/2,+pi/2]. The arc sine is also often called the inverse sine and is denoted by sin^{-1}(x).

  #include <math.h>
  #include <stdio.h>

  int main(void)
  printf("Arc sine of %f is %f.\n", val, asin(-1.0));
  return 0;

Arc sine of -1.000000 is -1.570796.