asin.c

#include "lib/math.h"
 
double asin_ipart(double t) {
    return pow(1.0 - pow(t, 2.0), -0.5);
}
 
double asin(double x) {
    if(x < -1.0 || x > 1.0) {
        return NAN;
    }
 
    if(x == 1.0) {
        return PI / 2;
    }
 
    return trapezoidal_rule(
        asin_ipart,
        0,
        x,
        ASIN_STEPS
    );
}