#include <stdio.h>
#include <math.h>
 
struct Triangle {
    double a;
    double b;
    double c;
};
 
int main(void) {
    struct Triangle x = { 5 , 5 , 5 };
    double s, area;
 
    s = (x.a + x.b + x.c) / 2.0;
    area = sqrt(s * (s - x.a) * (s - x.b) * (s - x.c));
 
    /* 出力 */
    printf("a: %.0f\n", x.a);
    printf("b: %.0f\n", x.b);
    printf("c: %.0f\n", x.c);
    printf("三角形の面積: %f\n", area);
 
    return 0;
}
 

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