NAME
    asin - returns arcsine of scalars and vectors.

SYNPOSIS
      float  asin(float a);
      float1 asin(float2 a);
      float2 asin(float2 a);
      float3 asin(float3 a);
      float4 asin(float4 a);
 
      half   asin(half a);
      half1  asin(half2 a);
      half2  asin(half2 a);
      half3  asin(half3 a);
      half4  asin(half4 a);
 
      fixed  asin(fixed a);
      fixed1 asin(fixed2 a);
      fixed2 asin(fixed2 a);
      fixed3 asin(fixed3 a);
      fixed4 asin(fixed4 a);

PARAMETERS
    a       Vector or scalar of which to determine the arcsine.

DESCRIPTION
    Returns the arcsine of *a* in the range [-pi/2,+pi/2], expecting *a* to
    be in the range [-1,+1].

    For vectors, the returned vector contains the arcsine of each element of
    the input vector.

REFERENCE IMPLEMENTATION
    asin for a float scalar could be implemented like this.

      // Handbook of Mathematical Functions
      // M. Abramowitz and I.A. Stegun, Ed.

      float asin(float x) {
        float negate = float(x < 0);
        x = abs(x);
        float ret = -0.0187293;
        ret *= x;
        ret += 0.0742610;
        ret *= x;
        ret -= 0.2121144;
        ret *= x;
        ret += 1.5707288;
        ret = 3.14159265358979*0.5 - sqrt(1.0 - x)*ret;
        return ret - 2 * negate * ret;
      }

PROFILE SUPPORT
    asin is supported in all profiles.

    Support in the fp20 is limited.

SEE ALSO
    the abs manpage, the acos manpage, the sin manpage, the sqrt manpage

