pku1927.cpp

这是ACM 方面的资料 是PKU的 北京大学的出来的

#include <stdio.h>
#include <math.h>

int main()
{
	double a, b, c, L, A, B, C, sum, area, p, R, r, PI, k, areall;
	int t = 0;
	PI = acos(-1);
	while (scanf("%lf %lf %lf %lf", &a, &b, &c, &L) != 0)
	{
		if (a == 0 && b == 0 && c == 0 && L == 0)
		{
			break;
		}
		
		sum = a + b + c;
		p = sum / 2;
		areall = sqrt(p * (p - a) * (p - b) * (p - c));
		if (sum <= L)
		{
			printf("Case %d: %.2lf\n", ++t, areall);
			continue;
		}

		A = acos((b * b + c * c - a * a) / (2 * b * c));
		B = acos((a * a + c * c - b * b) / (2 * a * c));
		C = acos((b * b + a * a - c * c) / (2 * b * a));
		
		k = 1 / tan (A / 2) + 1 / tan (B / 2) + 1 / tan (C / 2);

		R = p / k;
		
		if (R * PI * 2 >= L)
		{
			printf("Case %d: %.2lf\n", ++t, L * L / (4 * PI));
			continue;
		}

		r = (sum - L) / (2 * k - 2 * PI);
		
		area = areall + PI * r * r - r * r * k;
		printf("Case %d: %.2lf\n", ++t, area);
	}
	return 0;
}