三角形面积&外接圆&内切圆

三角形面积
4 * area = sqrt((a + b + c) * (a + b - c) * (a + c - b) * (b + c - a))
OR
(海伦公式)
s = (a +b + c) / 2.0
area = sqrt(s * (s - a) * (s - b) * (s - c))

外接圆半径
R = (a * b * c) / sqrt(4 * b * b - (b * b + c * c - a * a) * (b * b + c * c))

内切圆半径
r = sqrt((a + b + c) * (a + b - c) * (a + c - b) * (b + c - a)) / (2 * (a + b + c))

#include <cstdio>
#include <math.h>

int main(){
	int a, b, c;
	scanf("%d%d%d", &a, &b, &c);
	float area, s;
	s = (a + b + c) / 2.0;
	area = sqrt(s * (s - a) * (s - b) * (s - c)); 
	printf("%f\n", area);
	area = sqrt((a + b + c) * (a + b - c) * (a + c - b) * (b + c - a)) / 4.0;
	printf("%f\n", area);
	return 0;
}