#include <iostream.h>#include <stdio.h>#include <math.h> //////////////////函数--用卡丹公式解一元三次方程/////////////////void fun(double a,double b,double c,double d,   double *real_y1,double *real_y2,double *real_y3,   double *imag_y1,double *imag_y2,double *imag_y3){ double p,q,r,u,v,g,h,fai; p=(3.0*a*c-b*b)/(3*a*a); q=(2.0*pow(b,3.0)-9*a*b*c+27.0*a*a*d)/(27.0*pow(a,3.0)); r=b/(3.0*a); h=pow(q/2.0,2.0)+pow(p/3.0,3.0); g=sqrt(h); if(h>=0) {  if(-q/2.0+g<0)  u=-pow(fabs(-q/2.0+g),1.0/3.0);  else  u=pow((-q/2.0+g),1.0/3.0);  if(-q/2.0-g<0)  v=-pow(fabs(-q/2.0-g),1.0/3.0);  else  v=-pow((-q/2.0-g),1.0/3.0);  if(h==0)  {   *real_y1=u+v-r;            *imag_y1=0;      *real_y2=-(u+v)/2-r;       *imag_y2=0;   *real_y3=-(u+v)/2-r;       *imag_y3=0;  }  else  {    *real_y1=u+v-r;       *imag_y1=0;   *real_y2=-(u+v)/2;    *imag_y2=sqrt(3.0)*(u-v)/2;   *real_y3=-(u+v)/2;    *imag_y3=-sqrt(3.0)*(u-v)/2;  } } else {  fai=acos((-q/2)/(sqrt(pow(fabs(p),3)/27)));  *real_y1=2*sqrt(fabs(p)/3.0)*cos(fai/3.0)-r;  *real_y2=-2*sqrt(fabs(p)/3.0)*cos((fai+3.1415926)/3.0)-r;        *real_y3=-2*sqrt(fabs(p)/3.0)*cos((fai-3.1415926)/3.0)-r;  *imag_y1=0;   *imag_y2=0;    *imag_y3=0; }}//////////////////////////////////主函数//////////////////////////////// void main() {  double a,b,c,d;  double real_x1,real_x2,real_x3;  double *preal_x1=&real_x1;  double *preal_x2=&real_x2;  double *preal_x3=&real_x3;  double imag_x1,imag_x2,imag_x3;  double *pimag_x1=&imag_x1;  double *pimag_x2=&imag_x2;  double *pimag_x3=&imag_x3;  cout<<"请输入方程的系数a,b,c,d:"<<"\n"<<endl;  cout<<"系数a=";  cin>>a;  cout<<endl;  cout<<"系数b=";  cin>>b;  cout<<endl;  cout<<"系数c=";  cin>>c;  cout<<endl;  cout<<"系数d=";  cin>>d;  cout<<endl;  fun(a,b,c,d,preal_x1,preal_x2,preal_x3,pimag_x1,pimag_x2,pimag_x3);  cout<<"  "<<"   "<<"根的实部"<<"      "<<"根的虚部"<<"\n"<<endl;  printf("x1   %.5f      %.5f\n\n",real_x1,imag_x1);  printf("x2   %.5f      %.5f\n\n",real_x2,imag_x2);  printf("x3   %.5f      %.5f\n\n",real_x3,imag_x3); }

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