Approximating square root function using loops

Please help me solve this:

the "divide and average" method, an old-time method for approximating the square root of any positive number a, can be formulated as x=(x+a/x)/2. write a well-structured function to implement this alogrithm.

here is my first line:

function estSqrt= ApproxSqrt(a,tol)

a is the number whos square root i want to find

tol is the tolerance that must be greater than abs(xOld-xNew)/abs(xOld)

[Matt J]

I think you mean

x=(x+a/x)/2

[Char Jacobus]

yeah sorry

[Matt J]

Well, you have to write more than the first line of code in order to call it "help".

[Char Jacobus]

I can't seem to make this work for negative inputs of a

function estSqrt= ApproxSqrt(a,tol)
% function estSqrt= ApproxSqrt(a,tol)
e = 1;
x = a/2;
estSqrt = 1;
    if a == 0
    estSqrt = 0;
    end
    while e > tol
        xOld = x;
        x = (x+a/x)/2;
        e=abs((x - xOld)/x);
        estSqrt = x;
            if a < 0
               a = abs(a);
               estSqrt = x*1i;
            end
    end  
end

[Matt J]

I can't seem to make this work for negative inputs of a

Why would you need to?

Answer 1

[AKARSH KUMAR]

function estSqrt= ApproxSqrt(a,tol)

if a<0

msg='Can't calculate square root of negative number';

error(msg);

else if a==0

estSqrt=0;

else

e = 1;

x = a/2;

estSqrt = 1;

while e > tol

xOld = x;

x = (x+a/x)/2;

e=abs((x - xOld)/x);

estSqrt = x;

if a < 0

a = abs(a);

estSqrt = x*1i;

end

end

end

end