c++初学完整程序

#include<iostream>
#include<cmath>
using namespace std;

class Juxing
{
public:
Juxing(double a ,double b){c=a,d=b;};
double getS();
private:
double c,d;
};
 
double Juxing::getS()
{
double S;
S=c*d;
return S;
}



class Sanjiaoxing:public Juxing
{
public:
Sanjiaoxing(double a,double b,double c);
double getS();
private:
double e;
};