#include <stdio.h>
#include <math.h>
struct DATA{
double a;
double b;
double c;
double result;
};
int main(void) {
struct DATA data;
scanf("%lf %lf %lf",&data.
a,&data.
b,&data.
c); double s = (data.a+data.b+data.c)/2;
data.
result = sqrt(s
*(s
-data.
a)*(s
-data.
b)*(s
-data.
c)); printf("a=%f\nb=%f\nc=%f\n面積=%f\n",data.
a,data.
b,data.
c,data.
result); return 0;
}
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