atan.c

#include "lib/math.h"
 
double atan_ipart(double t) {
    return pow(1.0 + pow(t, 2), -1);
}
 
double atan(double x) {
    return trapezoidal_rule(
        atan_ipart,
        0,
        x,
        ATAN_STEPS
    );
}