median
don steward
mathematics teaching 10 ~ 16

## Wednesday, 11 August 2010

### why x?

one story:
Rene Descartes (1596 to 1650) popularised the idea of using letters from the back end of the alphabet for variables and letters from the front end of the alphabet for known constants (or parameters). That much is pretty definite.

Being French and writing in french, a typesetter would normally use many more y's and z's than x's, so they preferred to use the less frequently used letter: x.

Or so it is said.

another story:
is found as a TED talk by Terry Moore, who maintains that difficulties in translating from the Arabic al-shalan for 'the unknown thing'

( "Shei" first letter of al-shalan)

were resolved by using the Greek, Kai symbol

which later became the Latin, x

Others try to link it with the Greek word 'Xenos', a vague word indicating a stranger or alien or unknown.

Anyway, time to change this historical quirk to 'n' as a variable ('n' standing for any number). If we want two commonly used variables we can use 'm' and 'n' and if we want three we can use k, m and n.

This is a firm proposal for the planet.

We're fed up with x.