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22 lines
539 B
C++
22 lines
539 B
C++
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#include <stdio.h>
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#include <math.h>
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#define PI 3.141592653589793
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double square(double x)
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{
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return x * x;
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}
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int main(void)
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{
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double x1,y1,x2,y2,x3,y3;
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double a2,b2,c2;
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double r;
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while(scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3) != EOF)
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{
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a2 = square(x1 - x2) + square(y1 - y2);
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b2 = square(x1 - x3) + square(y1 - y3);
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c2 = square(x3 - x2) + square(y3 - y2);
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r = sqrt(c2/(1 - square(a2 + b2 - c2)/a2/b2/4))/2;
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printf("%.2f\n",2 * PI * r);
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}
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}
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