Article contents
Formulae for the convergents to some irrationals
Published online by Cambridge University Press: 01 August 2016
Extract
One of the questions that I set my students in a recent A level revision lesson was to express (√2 - 1)6 in the form a + b√2, where a and b are integers. While they were calculating the answer, it occurred to me that, as a consequence of the fact that (√2 - 1)n → 0 as n → ∞ (since 0 < √2 - 1 < 1 ), a and b could be used to give us a ‘good’ rational approximation to √2. Within a minute or so everyone agreed that (√2 - 1)6 = 99 - 70√2, allowing us to write √2 ≈ 99/70.
- Type
- Articles
- Information
- Copyright
- Copyright © The Mathematical Association 2004
References
- 2
- Cited by