How to find area of ​​a circle, triangle and square with the C programming language

# include <stdio.h>
# include <math.h>
# define PI 3:14

float CalculateAreaof​​aCircle (float radius) {
float K;
K = PI * (pow(radius,2));
return K;
}
float CalculateAreaof​​aTriangle (float U, float x) {
float S;
S = (U / 2) * X;
return S;
}
float  CalculateAreaof​​Square (float side) {
float V;
V = (pow(side,2));
return V;
}
float main (void) {
float R, U, X, T;
int choice;
printf ("Enter your choice: \ n");
printf ("1. Calculate the area of ​​a circle \ n");
printf ("2. Calculate the area of ​​the triangle \ n");
printf ("3. Calculate the square area \ n");
printf ("Select Match desire:");
scanf ("%d", &choice);
printf ("===================== \ n");
switch (choice) {
case 1:
printf ("Enter radius of circle:");
scanf ("%f", &R);
float e = CalculateAreaofaCircle (R);
printf ("Area of ​​circle with radius %.2f : %.2f", R, e); break;
case 2:
printf ("Enter the base triangle:");
scanf ("%f", &U);
printf ("Enter height triangle:");
scanf ("%f", &X);
float f = CalculateAreaof​​aTriangle (U, X);
printf ("Area of ​​triangles: %.2f", f) break;
case 3:
printf ("Enter side of square:");
scanf ("%f", &T);
float g = CalculateAreaof​​Square (T);
printf ("Area of ​​a square with sides of %.2f : %.2f", T, g); break;
default:
printf ("unknown option");
}
return 0;
}