UVA 11186(p349)----Circum Triangle

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#include<cstdio>#include<iostream>#include<cmath>#include<vector>using namespace std;const double pi=acos(-1.0);struct point{    double x,y;    point(double a=0.0,double b=0.0):x(a),y(b){}};vector<point> m;inline double change(double rad){    return (rad/180*pi);}inline double cross(double x1,double y1,double x2,double y2){    return (x1*y2-x2*y1);}inline double area(point a,point b,point c){    return fabs(cross(a.x-b.x,a.y-b.y,c.x-b.x,c.y-b.y)/2);}int main(){    int n,r;    while(scanf("%d%d",&n,&r)==2&&n)    {        m.clear();        double ans=0.0;        for(int i=0;i<n;i++)        {            double rad;            scanf("%lf",&rad);            double x=change(rad);            m.push_back(point(r*cos(x),r*sin(x)));        }        for(int i=0;i<n;i++)            for(int j=i+1;j<n;j++)                for(int k=j+1;k<n;k++)                   ans+=area(m[i],m[j],m[k]);        printf("%.0lf\n",ans);    }    return 0;}

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