Making 2-rays angles from rotation angles

There are two main ideas of what an angle is:

a) the amount of opening between two rays

b) the amount of a rotation

This applet shows how to get a 2-rays angle from a rotation:

• Use the center of the rotation (O) as the vertex of the angle.
• Pick a point on the object that is rotation, such as A.
• Call A' the rotation of A.
• Draw angle AOA'.

Susan Addington, Created with GeoGebra

Quadrivium

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