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A-Z Video List
Adjacent Angles share a common side and a  common vertex 
Angles ABD and Angles are CBD are adjacent angles
adjacent angles
Vertical Angles are angles that are opposite one another, and share a common vertex. Vertical angles are congruent.
vertical angles
Consecutive Angles also called Same Side Interior Angles are interior angles found on the same side of the transversal. If the intercepted lines are parallel, and the angles are a linear pair, these angles are supplementary.
consecutive angles
Alternate Interior Angles are found inside the intersected lines and on opposite sides of the transversal. These angles are congruent.
alternate interior angles
Alternate Exterior Angles are found outside the intersected lines, and on opposite sides of the transversal. These angles are congruent.
alternate exterior angles
Common Core Standard  7.G.4   7th Grade Math

Pairs of Angles

​∠A  or  ∠ABC
naming angles


An angle is formed when two lines (rays) meet at a common point called a vertex. A ray is a line with a start point but doesn’t have an endpoint. Angles can be named by this vertex. The angle symbol ∠ is used to write an angle mathematically. A common method for naming angles is by using three points. Two points for the rays and one for the vertex.

Naming Angles

#math gif classifying angles
white box/angles in geometry
In Geometry angles are classified according to their angle measure.  The main angle classifications are: acute angle, obtuse angle, right angle, reflex, and straight angle.

Types of Angles GIF

right angle/angle types
angle types/ supplementary angle
geometry angles complementary angle/classifying angles
congruent angle/classifying angles
Complementary Angles are two angles that their angle measure add to 90 degrees.
congruent angle angles geometry
Congruent Angles are two angles that have equal angle measure.
supplementary angle
Supplementary Angles are two angles that add to 180 degrees.
A Reflex Angles  measures greater than 180 degrees
reflex angle/classifying angles

Hi, welcome to Moomoomath. Today we are going to look at classifying angles.The first angle we are going to look at is a 90 degree angles that makes an L shape and the symbol is a square box in the corner. Then we have a straight angle which is straight across without an actual angle. It thinks of it as a straight line. Then you have an angle that measures smaller than 90 degrees and that is an acute angle. Then you have an angle that is larger than 90 but less than straight and that is an obtuse acute. So, let’s label those. This first one is 90 and that is your reference angle. You always want to be familiar with your 90 degree angle to see if you have one that is smaller. So that one is an acute angle. This one is larger than 90 degree and you can sketch in your L, if you want to, to compare it. That one is greater so it is obtuse. And a straight line is 180 degrees. It is two, 90 degree angles put together. So this is your straight angle. So you are always comparing to your 90 degree angle or your right angle. So that is how angle are classified. So let’s look at the rules of angles. OK, an acute angle is an angle that is less than 90 degrees. A right angle is equal to 90 degrees. Your right angle is your reference angle. Then you have an obtuse angle that is greater than 90 and a straight angle which is equal to 180 degrees. You can use a protractor to measure those. And when you measure the angle with a protractor you are going to take the dot on the protractor and line it up with the vertex. What is the vertex? It is the corner of the angle. You are going to line it up and read it from the bottom up from 0. There is another video on protractors and how to use those. This is how you classify angles. Hope this is helpful!

Classifying Angles in Geometry

Acute Angles measure from 0 to less than 90 degrees
Angles are measured from the vertex which is the point of intersection of the two lines.( Labeled A in this example)
Straight Line measures exactly 180 degrees

An Obtuse angle measures greater than 90 degrees and less than 180 degrees
A Right Angle measures exactly 90 degrees. The square at the vertex tells you it is a right angle.
types of angles acute angle
types of angles obtuse angle
straight line/angles

Classifying Angles

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Angled Pairs