I want to define straight using the definition of having 180 degrees, but how do you explain 180 degrees?

Also what types of symmetry are considered line symmetry?

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- Sep 8th 2010, 02:15 PMloutja35What is straight?
I want to define straight using the definition of having 180 degrees, but how do you explain 180 degrees?

Also what types of symmetry are considered line symmetry? - Sep 8th 2010, 02:38 PMPlato
First a comment. Many who have worked in axiomatic geometry do not like using ‘degrees’ as a measure of angles.

An angle is the union of two rays with a common endpoint; as in $\displaystyle

\angle BAC = \overrightarrow {AB} \cup \overrightarrow {AC} $

Nowwould be the case in which $\displaystyle C-A-B$.**a straight angle**

$\displaystyle A,~B,~\&~C$ are collinear and $\displaystyle A$ is between $\displaystyle B~\&~C$.