#include <stdio.h>
#include <math.h>    // For sqrt in triangle area
#define PI 3.14159   // Constant value of PI
 
int main() {
    int choice;
    float length, width, radius, side, base1, base2, height;
    float a, b, c;   // Sides of triangle
    float area, perimeter, circumference, s;
 
    // Display Menu
    printf("=== Geometry Calculator ===\n");
    printf("1. Rectangle (Area & Perimeter)\n");
    printf("2. Circle (Area & Circumference)\n");
    printf("3. Square (Area & Perimeter)\n");
    printf("4. Triangle (Area & Perimeter)\n");
    printf("5. Trapezium (Area)\n");
    printf("Enter your choice (1-5): ");
    scanf("%d", &choice);
 
    switch(choice) {
        case 1: // Rectangle
            printf("\nEnter length of rectangle: ");
            scanf("%f", &length);
            printf("Enter width of rectangle: ");
            scanf("%f", &width);
 
            area = length * width;
            perimeter = 2 * (length + width);
 
            printf("\nArea of Rectangle      = %.2f\n", area);
            printf("Perimeter of Rectangle = %.2f\n", perimeter);
            break;
 
        case 2: // Circle
            printf("\nEnter radius of circle: ");
            scanf("%f", &radius);
 
            area = PI * radius * radius;
            circumference = 2 * PI * radius;
 
            printf("\nArea of Circle          = %.2f\n", area);
            printf("Circumference of Circle = %.2f\n", circumference);
            break;
 
        case 3: // Square
            printf("\nEnter side of square: ");
            scanf("%f", &side);
 
            area = side * side;
            perimeter = 4 * side;
 
            printf("\nArea of Square      = %.2f\n", area);
            printf("Perimeter of Square = %.2f\n", perimeter);
            break;
 
        case 4: // Triangle
            printf("\nEnter sides of triangle (a, b, c): ");
            scanf("%f %f %f", &a, &b, &c);
 
            perimeter = a + b + c;
            s = perimeter / 2; // Semi-perimeter
            area = sqrt(s * (s - a) * (s - b) * (s - c)); // Heron's Formula
 
            printf("\nPerimeter of Triangle = %.2f\n", perimeter);
            printf("Area of Triangle      = %.2f\n", area);
            break;
 
        case 5: // Trapezium
            printf("\nEnter base1 of trapezium: ");
            scanf("%f", &base1);
            printf("Enter base2 of trapezium: ");
            scanf("%f", &base2);
            printf("Enter height of trapezium: ");
            scanf("%f", &height);
 
            area = 0.5 * (base1 + base2) * height;
 
            printf("\nArea of Trapezium = %.2f\n", area);
            break;
 
        default:
            printf("\nInvalid choice! Please select 1–5.\n");
    }
 
    return 0;
}