#include <stdio.h>
#include <math.h>
 
// 三角形の構造体定義
struct Triangle {
    double a;
    double b;
    double c;
};
 
// ヘロンの公式で面積を計算する関数
double calculateArea(struct Triangle t) {
    double s = (t.a + t.b + t.c) / 2.0;
    return sqrt(s * (s - t.a) * (s - t.b) * (s - t.c));
}
 
int main() {
    struct Triangle tri;
 
    // ユーザー入力
    printf("三角形の3辺を入力してください。\n");
    printf("辺a: ");
    scanf("%lf", &tri.a);
    printf("辺b: ");
    scanf("%lf", &tri.b);
    printf("辺c: ");
    scanf("%lf", &tri.c);
 
    // 面積計算
    double area = calculateArea(tri);
 
    // 結果出力
    printf("入力された三角形の辺の長さ: a = %.2f, b = %.2f, c = %.2f\n", tri.a, tri.b, tri.c);
    printf("三角形の面積: %.2f\n", area);
 
    return 0;
}

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