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In geometry, us give various names come different varieties of angles depending on the measure up of the provided angle: best angles, nearby supplementary angles, upright angles. Yet how execute we recognize which is which?

Let’s start with the basics.

You are watching: These are two angles that add up to 180° that share a common vertex.

If the measure up of the angle is precisely 90 degrees, it’s recognized as a ideal angle. If an edge is less than 90 degrees, that an acute angle. An angle better than 90 levels is an obtuse angle. If the measure up of an edge is equal to 180 degrees, it’s recognized as a right angle.

There are likewise names given to pairs that angles.


Vertical angles, or the contrary angles, room the two angles directly opposite each other when two straight lines cross (Figure 1).

Complementary angles room two angle that add to 90 levels (Figure 2).

Supplementary angles room two angle that include up to 180 degrees (Figure 3).

Adjacent angle vs. Nonadjacent Angles

Angles are nearby when lock share a usual side and a usual vertex.



Angles 1 and 2 are nonadjacent, while angles 3 and 4 room — they share a typical side and also vertex.

Adjacent Supplementary angles Defined

Now that we recognize the meanings of surrounding and nonadjacent angles, we deserve to see that adjacent supplementary angles are two angle that re-superstructure a side and vertex and include up to 180 degrees.

Using this definition, look at the diagram listed below to see which angles are surrounding supplementary.


Angles ABC and ABD are surrounding because lock share line segment abdominal muscle and crest B.

Angles EFG and also HIJ space not nearby because they nothing share any kind of common side.

However, the angle procedures in both bag of supplementary angle (ABC and ABD, and EFG and HIJ) still equal 180 degrees.

To review, that means EFG and HIJ are supplementary angles. However, only ABC and ABD are nearby supplementary angles.

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Recognizing surrounding Supplementary Angles

To recap, adjacent supplementary angle don’t simply share a side and also vertex but they also add up come 180 degrees. This angles generally show up in geometry proofs, therefore if you’re not sure, look for a right line intersected by one more line segment v the two angles sharing a common side and vertex.