Question regarding while loop

function y = approx_sqrt(x)
y = x;
while abs(y^2 - x) > 1e-7*x
    y = (x/y + y)/2

This is part of the code in my lecture class. I wonder what is the purpose of setting y = x at the begining?

Can anyone explain to me? Thank you so much.

[KSSV]

It is nothing but saving x into other vairable y. x is like an intital value; it is saved into y, there after value of y changes and gets updated.

Answer 1

[Alan Stevens]

(1) Because you need a value in the logic test: abs(y^2 - x) > ...

(2) Because you need an initial guess on the right-hand side of the Newton-Raphson expresssion: (x/y + y)/2

[xxtan1]

Thank you so much!