

Fun with Emacs Calc - rayvega
http://www.masteringemacs.org/articles/2012/04/25/fun-emacs-calc/

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quotemstr
Emacs calc is one of my favorite computer algebra systems: it can derive and
sum and integrate, numerically or symbolically. It can do unit conversions,
graph equations, and do geometry. It's really very neat and useful.

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derleth
To use this code in any serious capacity, remember the sign conventions: North
latitude and East longitude are both positive, South latitude and West
longitude are both negative.

It's utterly arbitrary but fairly universal.

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tikhonj
If you think about north as up and west as left, then it works out the same as
a coordinate plane, so it makes sense.

