#include <stdio.h>
#include <math.h>
 
struct Triangle {
    double a;
    double b;
    double c;
};
 
int main(void) {
    struct Triangle t;
 
    double p;
    double s;
 
    t.a = 5;
    t.b = 5;
    t.c = 5;
 
    p = (t.a + t.b + t.c) / 2;
 
    s = sqrt(p * (p - t.a) * (p - t.b) * (p - t.c));
 
    printf("a : %0.lf\n", t.a);
    printf("b : %0.lf\n", t.b);
    printf("c : %0.lf\n", t.c);
    printf("三角形の面積 : %f\n", s);
 
    return 0;
}
 
 

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