Real Life/Headscratchers/Math: Difference between revisions
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* Why does pi get a name, rather than 2*pi? You don't measure a circle by it's diameter; you do it by its radius. Nobody would ever use half the circumference. If you want a circle constant, make it the circumference divided by the radius.
** There are people that agree with you. Some of them came up with a name for 2pi. [http://tauday.com/ We call it tau.]
*** Which must annoy people who use ''tau'' for the golden ratio.
** Presumably to make the area equation, pi*r^2, easier to remember and use.
** It's a holdover from the Greek era, when people ''did'' measure a circle by its diameter, not quite having gotten out of that habit from the pre-compass days. Even the familiar formula for the area of a circle, pi*r^2, was originally put down by Archimedes as "diameter times circumference over four."
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