uva 12301 - An Angular Puzzle

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题意：如图,已知角ACB,角CAE, 角EAB, 角CBD, 角DBA (in degrees), 求角 DEA。

注意：在 Output 中，“If there is more than one solution, print "Multiple solutions"”这句话是迷惑你的，根本没有这种情况！

#include<iostream>#include<iomanip>#include<cmath>#define pi (2.0*asin(1.0))using namespace std;typedef struct point{    double x,y;    point(double xx=0,double yy=0):x(xx),y(yy){}}vector;vector operator - (point a,point b){    return vector(a.x-b.x,a.y-b.y);}point operator + (point a,vector b){    return point(a.x+b.x,a.y+b.y);}vector operator * (vector a,double b){    return vector(a.x*b,a.y*b);}double dot(vector a,vector b){    return a.x*b.x+a.y*b.y;}double len(vector a){    return sqrt(dot(a,a));}double angle(vector a,vector b){    return acos(dot(a,b)/len(a)/len(b));}double cross(vector a,vector b){    return a.x*b.y-a.y*b.x;}vector rot(vector a,double rad){    double c=cos(rad),s=sin(rad);    return vector(a.x*c-a.y*s,a.x*s+a.y*c);}point inter(point p,vector v,point q,vector w){    vector u=p-q;    double t=cross(w,u)/cross(v,w);    return p+v*t;}int main(){    double a,b,c,d,e,s;    point pa,pb,pd,pe;    pb.x=10;    while(cin>>a>>b>>c>>d>>e)    {        s=a+b+c+d+e;        if(s==0) break;        else if(s!=180) cout<<"Impossible"<<endl;        else        {            b*=pi/180;            c*=pi/180;            d*=pi/180;            e*=pi/180;            vector v=rot(pb-pa,b+c),w=rot(pb-pa,pi-d-e);            pd=inter(pa,v,pb,rot(pb-pa,pi-e));            pe=inter(pa,rot(pb-pa,c),pb,w);            double x=angle(pe-pd,pe-pa)*180/pi;            cout<<fixed<<setprecision(2)<<x<<endl;        }    }    return 0;}