Bisection method

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//cosx-3x+1
#include<iostream.h>
#include<math.h>
#include<iomanip.h>
void main()
{
         double x1,x2,x3,fx1,fx2,fx3,e;
         abc:
         cout<<"Enter Two Initial Approximation\n";
         cin>>x1>>x2;
         fx1=cos(x1)-(3*x1)+1;
         fx2=cos(x2)-(3*x2)+1;
         if(fx1*fx2<0)
         {
                  x3=(x1+x2)/2;
                  fx3=cos(x3)-(3*x3)+1;
         }
         else
         {
                 cout<<"Re-Enter The Root\n";
                 goto abc;
         }
         cout<<"Enter Epsilon\n";
         cin>>e;
         cout<<"x1"<<setw(15)<<"x2"<<setw(15)<<"fx1"<<setw(15)<<"fx2"<<setw(15)<<"x3"<<setw(15)<<"fx3"<<endl;
         cout<<x1<<setw(15)<<x2<<setw(15)<<fx1<<setw(15)<<fx2<<setw(15)<<x3<<setw(15)<<fx3<<endl;
         while((x3-x1)>e || (x3-x2)>e)
         {
                 if(fx1*fx3<0)
                 {
                          x2=x3;
                          fx1=cos(x1)-(3*x1)+1;
                          fx2=cos(x2)-(3*x2)+1;
                          x3=(x1+x2)/2;
                          fx3=cos(x3)-(3*x3)+1;
                          cout<<x1<<setw(15)<<x2<<setw(15)<<fx1<<setw(15)<<fx2<<setw(15)<<x3<<setw(15)<<fx3<<endl;
                 }
                 else if(fx2*fx3<0)
                 {
                          x1=x3;
                          fx1=cos(x1)-(3*x1)+1;
                          fx2=cos(x2)-(3*x2)+1;
                          x3=(x1+x2)/2;
                          fx3=cos(x3)-(3*x3)+1;
                          cout<<x1<<setw(15)<<x2<<setw(15)<<fx1<<setw(15)<<fx2<<setw(15)<<x3<<setw(15)<<fx3<<endl;
                 }
                 else if(x3==0)
                 {
                          cout<<x3<<"Required Root\n";
                 }
}
         cout<<"Required Root Is:="<<x3;
}