Talk:International System of Units/Archives/11/2009

This is an archive of past discussions about International System of Units. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

SI missing

Dear [type your name here],

Quick word about one "sort of unit" my physic teacher use to teach us: radians and steradians.

Best regards, virtualgot@hotmail.com —Preceding unsigned comment added by 61.173.98.133 (talk) 09:41, 10 November 2009 (UTC)

These used to be classed as Supplementary Units but are now Derived Units. They are both dimensionless ratios. E.g., a radian is the ratio of arclength (in metres) to radius (also in metres) and therefore the units are m/m, which equals 1. They can be included or excluded when they add clarity to a measure. For example, angular velocity can be rad/s or simply s^-1. DGERobertson (talk) 00:08, 11 November 2009 (UTC)