C++ help i need help with a program im trying to get to work

[damianbloch49]

#include <iostream>
 #include <cmath>
 #include <iomanip>
 
using namespace std;
 
const double PI = 3.1416;
 

// Student adds code for distance function prototype
 double distance (char ch);
 // Student adds code for radius function prototype
 double radius (char ch);
 // Student adds code for circumference function prototype
 double circumference (char ch);
 // Student adds code for area function prototype
 bool area (char ch);
 

int main()
 {
 double x1, x2, y1, y2;
 double circleRadius;
 
cout << fixed << showpoint << setprecision(2);
 
cout << "Enter the x and y coordinates of the center of the circle: ";
 cin >> x1 >> y1;
 cout << endl << endl;
 
cout << "Enter the x and y coordinates of a point on the circle: ";
 cin >> x2 >> y2;
 cout << endl << endl;
 
circleRadius = sqrt(x2 - x1)*2 + (y2-y1)*2; // Student adds code to use radius function.
 
cout << "Radius = " << circleRadius << endl;
 cout << "Diameter = " << 2 * circleRadius << endl;
 cout << "Circumference = " << 2 * PI * circleRadius << endl;/* Student adds code to use circumference function */
 cout << "Area = " << PI * pow(circleRadius, 2) << endl;/* Student adds code to use area function */
 
return 0;
 }
 // Student adds code for distance function header and definition
 double distanceFormula(sqrt(x2 - x1)*2 + (y2 - y1)*2)
 {
 double distance;
 return distance;
 }
 

// Student adds code for radius function header and definition
 double radiusFormula(circumference / 2 * PI)
 {
 double radius;
 return radius;
 }
 

// Student adds code for circumference function header and definition
 double circumferenceFormula(2 * PI * circleRadius * 2)
 {
 double circumference;
 return circumference;
 }
 

// Student adds code for area function header and definition
 double areaFormula(PI * circleRadius * 2)
 {
 double area;
 return area;
 }

this is what i got so far but i need help with like the formula and what to put in it cause i dont think i

[wildblue]

It looks like you're trying to put the formula in the parameters? The code then just declares a variable area, doesn't give it a value, and returns whatever uninitialized value it has.

double areaFormula(PI * circleRadius * 2)
 {
 double area;
 return area;
 }

Here's just one example of a function that calculates the area of a circle given a radius, and how it could be called from the main function to print out the value it calculates.

const double PI = 3.1416;

int main()
{
    double radius = 10.5;
    std::cout << "Area of circle with radius " << radius << " is " << calculateArea(radius) << std::endl;  
    
    return 0;
}

double calculateArea (double r)
{
    return PI*r*r;
}

[damianbloch49]

thanks but im still working on it and it still says there are errors in it