adjacent angles
http://www.mathsisfun.com/geometry/adjacent-angles.html
Adjacent angles are a pair of angles that have a common vertex and a common side but do not overlap. In other words, they share a common endpoint and a common side extending from that endpoint, but they do not share any interior points.
To determine if two angles are adjacent, you can follow these steps:
1. Identify the common vertex: Look for the point where the two angles meet. It will be the endpoint of both angles.
2. Check for the common side: Determine if the two angles share a side that extends from the common vertex. The side should be in the same plane as the angles.
3. Verify that the angles do not overlap: Ensure that the interior of one angle does not intersect with the interior of the other angle. If they overlap or share points inside the angles, they are not adjacent angles.
4. If the two angles satisfy all of the above conditions, then they are adjacent angles.
Adjacent angles are commonly seen in geometric shapes, such as triangles, quadrilaterals, or polygons. For example, in a rectangle, adjacent angles are formed at each corner where two sides meet.
Remember, adjacent angles are different from vertical angles and linear pairs. Vertical angles are formed by the intersection of two lines and are not adjacent, while linear pairs are adjacent angles that are supplementary (the sum of their measures is 180 degrees).