input value
inverse coversed sine
var v = acoversin( 0.0 );
// returns ~1.5708
var v = acoversin( 3.141592653589793/2.0 );
// returns ~-0.6075
var v = acoversin( 3.141592653589793/6.0 );
// returns ~0.4966
var v = acoversin( NaN );
// returns NaN
Computes the inverse coversed sine.