I am a newbie in c++ and I am quite confused in programmer – defined functions.

It shows these errors

40 [Error] cannot convert ‘double’ to ‘double(double, double)’ in assignment

40 [Error] assignment of function ‘double total_area(double, double)’

I cannot enter total_area = cross_area + side_area;

If i try to remove the double, it results to more errors

I cant find any information in youtube taht seems helpful or wvwn google

```
// P33_2.cpp This program illustrates the local and global variables and call-by-value.
// This program computes the side area and the cross section area of a cylinder
#include<iostream>
#include<cmath>
using namespace std;
const double PI = 3.14159; // This variable is defined globally, known to all functions in this program as PI
double cross_area(double r); // Function prototype for function cross_area
double side_area(double r, double h); // Function prototype for function Side_area
double total_area(double cross_area, double side_area);
int main(void)
{
double h, r; //variables local to the main function
cout << "Enter the radius and the height of the cylinder in Cm <Enter> ";
cin >> r >> h;
cout << endl;
cout << "Before I do any computation or call any function, I want to let you know that n";
cout << "you have entered r = " << r << " and h = " << h << "." << endl;
cout << "I am planning to use inch, thus in the first function, I will convert r, and " << endl;
cout << "in the second one I will convert h n";
cout << "The cross section area of the cylinder is " << cross_area(r) << " inch-sqr endln";
cout << "The side area of the cylinder is " << side_area(r,h) << " inch-sqr nn";
cout << "The total surface area is "<< total_area << "inch-sqr n n";
return 0;
}
double cross_area(double r)
{
//Cross secion area includes the disks at the bottom and the top
r = r * 0.3937; // converting r to inch
return 2*PI*pow(r,2);
}
double side_area(double r, double h)
{
double area; //variable local to Side_area function
h = h * 0.3937; // converting h to inch
area = 2*PI*r*h;
return area;
}
double total_area(double cross_area, double side_area)`enter code here`
{
total_area = cross_area + side_area;
return 0;
}
```

Source: Windows Questions C++