Main Learning Goal and Core Concepts: Students will be able to write and identify specific angles as well as add angles when given a missing angle.

## Vocabulary

#### Ray

A line of indefinite length extending from an end point in one direction

#### Vertex

A point where two or more rays or the arms of an angle meet

## Lesson Brief

• Like with other math problems, we use symbols to abbreviate what we are asked to do
• Example: x, ÷, +, -, =
• With angles, we use the symbol “∠”

Example: Suppose we have a vertex like the following. How would we read it if we were asked to find angle B? • We could label it as m∠B (“measurement of angle B”) or m∠ABC (“measurement of angle A, B, C [note how the B is in the middle]).
• The “m” lets us know that we are trying to find the degree angle of B.
• Note how this vertex can only have one angle that can be extracted.

How do we read angles in more complex situations?

Example: • This can be a little more complex. We have a vertex where two different angles can be extracted.
• We have four different points, but we are focused on point B.
• So, how do we name both angles?
• ∠ABD or ∠DBA
• ∠CBD or ∠DBC
• Again, note how the B point is in the middle. This let’s us know that our main focus is B. Also, since we have two different angles here, it is important to include all points that are a part of the specific angle.

• If we are given the degrees of the angles, we simply add and make sure we include our degree symbol.

What if we are missing the degree of an angle in an addition problem?

• We can:
• look for symbols within the vertex (right angle/90°)
• use our previous knowledge of angles (180° = line, 360° = circle)
• use the surrounding angle degrees to find the missing angle
• look for keywords if we are dealing with a word problem

Notes:

• It is important to thoroughly read the angles and their measurements. Doing so helps us identify what angle(s) we are given and what angle(s) we need to find.

If you would like to look at additional examples, you can find them linked here and here.

‘Ray’ Definition: Source
Vertex’ Definition: Source