# Adjacent

The term "adjacent" is often used to describe angles. It is also used to describe the sides of polygons.

## Adjacent angles

Adjacent angles are two angles in a plane that have a common vertex and a common side. They do not have any common interior points. In other words, they do not share any "inside space."

Example:

The 3 roads above form two adjacent angles. The two angles formed share a common side of Park Road and the intersection of the 3 roads is the common vertex for the 2 adjacent angles. In this case, it would probably be wise to put a traffic signal at the vertex.

Knowing that 2 angles are adjacent is useful for finding the measure of one of the adjacent angles given the measure of the other.

Example:

In the diagram above ∠POM = 67° and ∠MON=52°. Since ∠PON and ∠MON are adjacent angles the measure of their sum is ∠POM,

∠PON + ∠MON = ∠POM |

∠PON + 52° = 67° |

∠PON = 15° |

## Adjacent sides

Adjacent sides are two sides of a polygon or other shapes that have a common vertex.

In the triangle above, and are adjacent sides since they share the same vertex, B. and and and are also adjacent sides.

In the parallelogram above, sides and , and are two examples of adjacent sides since they have common vertices. In contrast, sides and and and are not adjacent sides since they do not share a vertex.