ardupilot/libraries/AP_Math/AP_Math.cpp

#include "AP_Math.h"

// a varient of asin() that checks the input ranges and ensures a
// valid angle as output. If nan is given as input then zero is
// returned.
float safe_asin(float v)
{
	if (isnan(v)) {
		return 0.0;
	}
	if (v >= 1.0) {
		return PI/2;
	}
	if (v <= -1.0) {
		return -PI/2;
	}
	return asin(v);
}

// a varient of sqrt() that checks the input ranges and ensures a
// valid value as output. If a negative number is given then 0 is
// returned. The reasoning is that a negative number for sqrt() in our
// code is usually caused by small numerical rounding errors, so the
// real input should have been zero
float safe_sqrt(float v)
{
	if (isnan(v) || v <= 0.0) {
		return 0.0;
	}
	return sqrt(v);
}