C代码
注意只需要任意两边之和大于第三边即可
#include <stdio.h>
#include <Math.h>
int main() {
double A, B, C;
scanf("%lf %lf %lf", &A, &B, &C);
if (A + B > C && A + C > B && B + C > A) //三角形任意两边大于第三边
printf("Perimetro = %.1lf", A + B + C);
else
printf("Area = %.1lf", (A + B) * C / 2);
return 0;
}