Straight angleAlso Flat Angle
Definition: An angle
whose measure is exactly 180° - a straight line
Adjust the angle
below by dragging an orange dot and see how the angle ∠
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.
Related angle topics
(C) 2009 Copyright Math Open Reference. All rights reserved
Math Open Reference now has a Common Core alignment.
See which resources are available on this site for each element of the Common Core standards.
Check it out