`
#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
double A, B, C;
cin >> A >> B >> C;
printf("TRIANGULO: %.3lf\n", (1.0 / 2) * A * C);
//直接写(1/2)会报错,因为(1/2)= 0[······1]
//(1/2)改为浮点数(1.0/2)或(1/2.0)
printf("CIRCULO: %.3lf\n", 3.14159 * C * C);
printf("TRAPEZIO: %.3lf\n", /*(1.0 / 2)*/0.5 *(A + B) * C);
//将(1/2)直接改为 0.5 也可以
printf("QUADRADO: %.3lf\n", B * B);
printf("RETANGULO: %.3lf\n", A * B);
return 0;
}
`