Foxmaths! 2.0

July 3, 2008

Approximating Irrationals

Filed under: Maths — Tags: , — Fox @ 9:00 am

Let’s suppose, for a moment, that the square root of 2 were rational. Then there would be a pair of numbers a and b such that

\frac{a}{b} = \sqrt{2}

We can manipulate that in the following way,

a = b*\sqrt{2}

a - b*\sqrt{2} = 0

So, if the square root of 2 were rational, we would be able to find integers a and b to solve the above equation. Of course, it isn’t, so we can’t.

But what if it were something very very close to zero? Say the expression came out to e, where e was very very small. In that case …

a - b*\sqrt{2} = e

a = e + b*\sqrt{2}

\frac{a}{b} = \frac{e}{b} + \sqrt{2}

Looking at the above, if e is very very close to 0 and b is some integer, then e/b will be even closer to 0. Which means that a/b is only very slightly off from the square root of 2.

The question then is how to find such a and b so as to yield very small e.
(more…)

Blog at WordPress.com.