Answer:
#include <iostream> 
using namespace std; 
float calculate_sq_inches_of_good_pizza(float diameter) { 
 float radius= diameter/2; 
 float pi=3.14;
 float area; 
 area = pi*(radius*radius );
 return area;
} 
int main() { 
 float d;
 cout<<"enter the diameter of pizza"<<endl;
 cin>>d>>endl;
 float area_of_pizza = calculate_sq_inches_of_good_pizza(); 
 return 0; 
}
Step-by-step explanation:
Above program is written in C++ language which has function namely float calculate_sq_inches_of_good_pizza(float diameter). This will calculate area of pizza from given diameter and return it to main() function.
As we know pizza is circle and area of circle is equal to:
Area = π * radius*radius 
π =pi=3.14
and we have calculated radius from given diameter
radius = diameter/2;
If you only want function not whole program than ignore main () function and only consider float calculate_sq_inches_of_good_pizza(float diameter) function  which is in ITALIC notation.