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Good Bisection Method Output

newton123 (32)
Hello everyone, my code below solve for the root of the function f(x) = .5x - sin(x). It is working fine but i want to add a little bit to it.

I want to implement the following output without using printf(). How would i implment it? please help me modify my code.. i'm struggling.. thanks!:
_____________________________________________________________________

Iteration     x+          x-        f(x+)        f(x-)     midpoint
_____________________________________________________________________
   1           4           2       -.08093       .9568         3
   2           3           2        .0088       -.8093         2.5
   3           3           2.5      .0088        .65153        2.75
   4           2.75        2.5      .99333       .65153        2.625
   .
   .
   .
______________________________________________________________________

The approximate root is: 2.625



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  #include <iostream>
#include <math.h>
using namespace std;

double f(double);

int main()
{
    double a, b, lv, rv, midv, mid, root, tol;
    
    cout << "Enter a: ";
    cin >> a;
    cout << "Enter b: ";
    cin >> b;
    cout << "Enter tolerable error: ";
    cin >> tol;
    
  do
   {
       mid=(a+b)/2;
       rv=f(b);
       lv=f(a);
       midv=f(mid);
       if(midv==0)
        {
            root=mid;
			break;
		}
       if(midv*lv<0)
		{
			b=mid;
		}
       else
			a=mid;
    }while((b-a)>tol);
   root=(a+b)/2;
   cout << " The Root is approximately: ";
   cout << root;
   
   cin.get();
   cin.get();
   return 0;
}
double f(double x)
{
       return .05*x-sin(x);
}
Last edited on
kbw (9488)
Are you sure this is right?
if(midv*lv<0)
newton123 (32)
yes. i already tried running it.. it works fine.. my problem is how to implement the output above... please help me modify my code.. thaxnks!
ValliusDax (70)
The iomanip library has some things that would be useful.

Here's an example:

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#include <iomanip>
#include <iostream>

using namespace std;

int main()
{
	cout << "Iteration     x+          x-        f(x+)        f(x-)     midpoint" << endl;
	cout << "_____________________________________________________________________" << endl;

 int iteration = 0;
 int xplus = 6666666; 
 int xneg = 999999;
 double fxplus= .999999;
 double fxneg = .999;
 double midpoint = 5.5;

 cout << setw(5) << iteration << ' '
       << setw(10) << xplus    << ' '
       << setw(11) << xneg     << ' '   
       << setw(12) << fxplus   << ' ' 
       << setw(12) << fxneg    << ' '   
       << setw(10) << midpoint << ' '
       << endl;
 
	return 0;
}
newton123 (32)
problem solved! Thanks much!
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