too few arguments in function call error

too few arguments in function call error

Doing an assignment to calculate the area and volume of different shapes.
Stuck is an understatement. Get an error claiming 'showMenu': function
does not take 0 arguments & a also a too few arguments in function call
error. Any pointers on how to fix this?
#include <iostream>
#include <iomanip>
using namespace std;
//Functions
void showMenu(int &);
double area (double, double);
double area (double);
double volume (double, double, double);
double volume (double);
const double PI = 3.14;
int main()
{
int choice;
double area, volume, length, width, radius, height;
const double PI = 3.14;
do
{
showMenu();
cin >> choice;
if (choice < 1 || choice > 5 )
{
cout << "Please select a valid choice of 1-5: " << endl;
cin >> choice;
}
else if (choice == 1)
{
double tarea(area);
cout << "Enter the length: ";
cin >> length;
cout << "Enter the width: ";
cin >> width;
cout << "The area of the rectangle is: " << tarea << endl;
}
else if (choice == 2)
{
double tarea(area);
cout << "Enter the radius: ";
cin >> radius;
cout << "The area of the circle is: " << tarea << endl;
}
else if (choice == 3)
{
double tvolume (volume);
cout << "Enter the length: ";
cin >> length;
cout << "Enter the width: ";
cin >> width;
cout << "Enter the height: ";
cin >> height;
cout << "The volume for a box is: " << tvolume << endl;
}
else if (choice == 4)
{
double tvolume (volume);
cout << "Enter the radius: ";
cin >> radius;
cout << "The volume of a sphere is: " << endl;
}
}
while (choice != 5);
return 0;
}
void ShowMenu(int &choice)
{
cout << "1. Calculate the area of a rectangle";
cout << "2. Calculate the area of a circle";
cout << "3. Calculate the volume for a box";
cout << "4. Calculate the volume of a sphere";
cout << "5. Quit";
}
double area (double length, double width)
{
double tarea = length * width;
return tarea;
}
double area (double radius)
{
double tarea = PI * (radius * radius);
return tarea;
}
double volume (double length, double width, double height)
{
double tvolume = length * width * height;
return tvolume;
}
double volume (double radius)
{
double tvolume = (4/3) * PI * (radius * radius * radius);
return tvolume;
}