In details

Null angle and shallow angle

Notice now two cases in which the straight lines of the same origin are contained in the same line. In such cases, angles are also formed.

Null angle and one turn angle

  • The half straight coincide. We have there null angle and the angle of a turn.

Shallow or half turn angle

  • The half straight do not match. We have two shallow angles or of U turn.

We can then establish that:

Angle is the region of the plane bounded by two semi-straights that have the same origin. Next: Measuring an Angle