Доработать класс Equation

class equation
{
private:
    double x;
    double y;
    double z;
    double al;
public:
    equation();
    equation(double, double, double);
    void solve();
    double getResult();
    ~equation();
};

#include "equation.h"
#include <cmath>
 
 
 
 
equation::equation(double x, double y, double z)
{
    this->x = x;
    this->y = y;
    this->z = z;
}
 
 
 
void equation::solve()
{
    this->x = x;
    this->y = y;
    this->z = z;
    this->al = al;
    al = log(pow(y, -sqrt(abs(x))))*(x - (y / 2)) + pow(sin(atan(z)), 2);
}
 
double equation::getResult()
{
    double result = al;
    return result;
}
 
equation::~equation()
{
 
}

#include <cmath>
#include "equation.h"
#include <iostream>
 
using namespace std;
 
int main()
{
    equation p(-15.246, 4.642*pow(10, -2), 20.001*pow(10, 2));
 
    p.solve();
    cout << "alpha = " << p.getResult() << endl;
    system("pause");
    return 0;
}