# making sqrt file without using sqrt function

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zot il 9 Apr 2023
Modificato: Sam Chak il 10 Apr 2023
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Steven Lord il 9 Apr 2023
This sounds like a homework assignment. If it is, show us the code you've written to try to solve the problem and ask a specific question about where you're having difficulty and we may be able to provide some guidance.
If you aren't sure where to start because you're not familiar with how to write MATLAB code, I suggest you start with the free MATLAB Onramp tutorial to quickly learn the essentials of MATLAB.
If you aren't sure where to start because you're not familiar with the mathematics you'll need to solve the problem, I recommend asking your professor and/or teaching assistant for help.

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### Risposte (2)

Walter Roberson il 10 Apr 2023
Each step iteration improves the precision, so with 9 digits as the target precision, you can take 9 iterations.
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Sam Chak il 10 Apr 2023
Modificato: Sam Chak il 10 Apr 2023
Hi @zot
Edit: Since you didn't provide more info, then I'd suggest Newton–Raphson method.
From the definition
it can be rearranged to
to repeat the iteration until the required accuracy is achieved. You can modify Newton–Raphson code for calculating the square root of a real number. Also, address the situations when the initial guess is very far from the real solution (usually happens for very large real number).
The code should generate result like this:
format long g
fun = inline('x^2 - 101', 'x');
x0 = 5; % initial guess
TolX = 1e-9;
[x, err, xx] = modNRsqrt(fun, x0, TolX)
x =
10.0498756211209
err =
0
xx = 1×7
5 12.6 10.3079365079365 10.0531059195057 10.0498761401062 10.0498756211209 10.0498756211209
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