Man you've done most of the work, just call your function in main, here is the code with some changes:

C++ Syntax (Toggle Plain Text)

#include <iostream>
#include <iomanip>
 
const float PI= 3.14;
 
float circle_area(float &radius);
 
float circle_area(float &radius)
{
	using namespace std;
 
	float area= PI*radius*radius;
	cout<< "The area of the circle with radius "<<radius<< " is: "<< area << setprecision(2) << endl;
	return (area);
}
 
int main()
{
	using namespace std;
 
	float radius;
	cout<< "What is the radius of the circle:> ";
	cin >> radius;
	circle_area(radius);
	return 0;
}

#include <iostream> #include <iomanip> const float PI= 3.14; float circle_area(float &radius); float circle_area(float &radius) { using namespace std; float area= PI*radius*radius; cout<< "The area of the circle with radius "<<radius<< " is: "<< area << setprecision(2) << endl; return (area); } int main() { using namespace std; float radius; cout<< "What is the radius of the circle:> "; cin >> radius; circle_area(radius); return 0; }

Intel

That will work but a function should really stick to only doin one thing... either calculation or cout, since this is not a complex task.

C++ Syntax (Toggle Plain Text)

float circle_area(float radius)
{
	return PI * radius * radius;
}

float circle_area(float radius) { return PI * radius * radius; }

Then do the cout's in main