Straight angleAlso Flat Angle
Definition: An angle whose measure is exactly 180°  a straight line
Try this
Adjust the angle below by dragging an orange dot and see how the angle ∠ABC behaves.
Note that it is a Straight Angle only when it is exactly 180°
Straight (or Flat) angles are formed when the legs are pointing in exactly opposite directions. The two legs
then form a single straight line through the vertex of the angle. The measure of a flat angle is thus always 180°
Types of angle
Altogether, there are six types of angle as listed below. Click on an image for a full description of that type and a corresponding interactive applet.
Other angle topics
General
Angle Types
Angle relationships
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