#include <stdio.h>
#include <math.h>
struct Triangle {
    double a;
    double b;
    double c;
};
 
int main(void) {
    struct Triangle t;
    double s;
    double area;
    printf("aを入力: ");
    scanf("%lf", &t.a);
    printf("bを入力: ");
    scanf("%lf", &t.b);
    printf("cを入力: ");
    scanf("%lf", &t.c);
    s = (t.a + t.b + t.c) / 2.0;
    area = sqrt(s * (s - t.a) * (s - t.b) * (s - t.c));
    printf("a : %.0f\n", t.a);
    printf("b : %.0f\n", t.b);
    printf("c : %.0f\n", t.c);
    printf("三角形の面積 : %f\n", area);
 
    return 0;
}
 

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