Editing Angle (section)

=== Notation ===
[[File:Angle diagram.svg|thumb|300x300px|<math>\angle BAC</math> is formed by rays <math>\vec{AB}</math> and '''<math>\vec{AC}</math>'''.  '''<math>\theta</math>''' is the conventional measure of <math>\angle BAC</math> and '''<math>\beta</math>''' is an alternative measure.]]
In geometric figures and [[Expression (mathematics)|mathematical expressions]], it is common to use [[Greek letter]]s (<var>α</var>, <var>β</var>, <var>γ</var>, <var>θ</var>, <var>φ</var>,&nbsp;.&nbsp;.&nbsp;.&nbsp;) or lower case Roman letters (''a'',&nbsp;''b'',&nbsp;''c'',&nbsp;.&nbsp;.&nbsp;.&nbsp;) as [[Variable (mathematics)|variables]] denoting the size of an angle.{{sfn|Aboughantous|2010|p=18}} The Greek letter {{math|[[Pi (letter)|π]]}} is typically not used for this purpose to avoid confusion with the [[Pi|circle constant]].

An angle symbol (<math>\angle</math> or <math>\widehat{ \quad }</math>) with three defining points may also identify angles in geometric figures. For example, <math>\angle BAC</math> or <math>\widehat{BAC}</math> denotes the angle with vertex A formed by the [[ray (geometry)|rays]] AB and AC. Where there is no risk of confusion, the angle may sometimes be referred to by a single vertex alone (in this case, "angle A").

Conventionally, angle size is measured "between" the sides through the interior of the angle and given as a [[Magnitude (mathematics)|magnitude]] or [[Scalar (physics)|scalar quantity]] without direction. At other times it might be a measure through the exterior of the angle or indicate a direction of measurement (see ''{{section link|#Signed angles}}'').