while loop

[devilsangels287]

Hey guys I have a problem with this while loop, its not working properly and I think that I might be typing it wrong but I don't how. please help me! Thanks... Anyways this is a calculator which is suppose to find the approximated square root value and using this algorithm, it is suppose to work. However in the while loop it apparently doesn't work for me.

Heres the code I put in:

 
#include <stdio.h>
 
int main ()
{
 
   double second, diff;
   double first = 1.0;     /* Given */
   double number;
 
   printf("please enter the number: ");
   scanf("%lf", &number);
 
/* the formula that I am suppose to use to find the approx sqrt*/
 
   second = .5 * (first + number/first);
   diff = first - second;
 
/* while loop is suppose to run until the difference is less than .005*/
   while (diff < .005)
   {
/* since the diff is greater than .005, we put in second into first  and then reiterating the same equation again*/
      first = second;
      second = .5 * (first + number/first);
      diff = first - second;
   }
 
   printf("\n%lf\n", second);
   return 0;
}
 
 

And when I plug in "3" for example, it comes up with 1.75, which it is suppose to be 1.73. But i have no idea how to change the loop to make that work. Thanks for helping!

[Ganon11]

Something is wrong with your logic...For instance, when I run your program with the value 25, it gives me the answer as 7.461538. I suspect it's a problem with using number inside the loop, rather than a problem with the loop itself.

[sicarie]

What do first and second stand for? Should you be resetting their values after the loop? I'd add a few cout statements in there and check what values are in all the variables each time you loop.

[Ganon11]

I'd add a few cout statements in there and check what values are in all the variables each time you loop.

Or printf, since this code looks very C-ish to me. :D

[sicarie]

Or printf, since this code looks very C-ish to me. :D

Heh, yeah, that would work too... Whoops :/