How do you approximate 2/sqrt323?

1 Answer
Jul 6, 2015

Use an iterative method to get a good rational approximation for sqrt(3)3 then use that to calculate 2/sqrt(3)23 to get (say)

2/sqrt(3) ~= 2/(97/56) = 112/97 ~= 1.1552329756=112971.155

Explanation:

Start with a reasonable approximation a_0 = 2a0=2 for sqrt(3)3.

Then iterate using the formula:

a_(i+1) = (a_i^2+3)/(2a_i)ai+1=a2i+32ai

a_1 = (a_0^2+3)/(2a_0)a1=a20+32a0

=(2^2+3)/(2*2)=22+322

=7/4=74

a_2 = (a_1^2+3)/(2a_1)a2=a21+32a1

=((7/4)^2+3)/(2*7/4)=(74)2+3274

=(49/16+48/16)/(7/2)=4916+481672

=97/56=9756

We will stop here, but if you want more accuracy, just iterate again.

In general, to find the square root of nn, pick a reasonable first guess as a_0a0, then iterate using:

a_(i+1) = (a_i^2+n)/(2a_i)ai+1=a2i+n2ai