Определить, находится ли точка с координатами (x,y,z) внутри шара

#include <iostream>
struct Sphere
{
    double x0;
    double y0;
    double z0;
    double R;
public:
    Sphere() :x0(0.0), y0(0.0), z0(0.0), R(1.0) {};
    Sphere(double x0_, double y0_, double z0_, double R_) :
        x0(x0_), y0(y0_), z0(z0_), R(R_) {};
    bool Inside(double x, double y, double z)
    {
        double dx = x - x0;
        double dy = y - y0;
        double dz = z - z0;
        double r2 = dx * dx + dy * dy + dz * dz;
        return r2 <= R * R;
    }
};
 
int main()
{
    double x, y, z;
    std::cout << "Enter coordinates of point:" << std::endl;
    std::cout << "\tx = "; std::cin >> x;
    std::cout << "\ty = "; std::cin >> y;
    std::cout << "\tz = "; std::cin >> z;
 
    Sphere sp1; // Create sphere with center (0,0,0) and radius R=1
    if (sp1.Inside(x, y, z))
        std::cout << "Point is inside sphere 1";
    else
        std::cout << "Point is not inside sphere 1";
 
    std::cout << std::endl;
 
    Sphere sp2(-1, 3, -4, 10); // Create sphere with center (-1,3,-4) and radius R=10
    if (sp2.Inside(x, y, z))
        std::cout << "Point is inside sphere 2";
    else
        std::cout << "Point is not inside sphere 2";
 
    return 0;
}