Oriented Side

<p>An oriented side AB = {A,B} is an <i>ordered</i> (comma separated) set of two points (relating to an origin).

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Signed area is:

s(AB)&#160;≡ s(OAB)

&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;= 1/2 OA × OB

Note:

s(BA = -s(AB)</p>