Recognizing Angles


With our Recognizing Angles lesson plan, students learn how to recognize and identify right, obtuse, and acute angles. Students practice identifying each type by sight and answer questions about them as a part of this lesson.

Included with this lesson are some adjustments or additions that you can make if you’d like, found in the “Options for Lesson” section of the Classroom Procedure page. One of the optional additions to this lesson is to add an art project to this lesson by having students use a certain number of angles to create a piece of art, like a painting or picture.

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What our Recognizing Angles lesson plan includes

Lesson Objectives and Overview: Recognizing Angles teaches students what angles are, and how to recognize different types of angles, such as obtuse and acute, by sight. At the end of the lesson, students will be able to define an angle, explain how they are formed, and identify the basic concepts of angle measurement. This lesson is for students in 4th grade.

Classroom Procedure

Every lesson plan provides you with a classroom procedure page that outlines a step-by-step guide to follow. You do not have to follow the guide exactly. The guide helps you organize the lesson and details when to hand out worksheets. It also lists information in the blue box that you might find useful. You will find the lesson objectives, state standards, and number of class sessions the lesson should take to complete in this area. In addition, it describes the supplies you will need as well as what and how you need to prepare beforehand. The only supplies you will need for this lesson are the handouts. To prepare for this lesson ahead of time, you can pair the students for the activity and copy the handouts.

Options for Lesson

Included with this lesson is an “Options for Lesson” section that lists a number of suggestions for activities to add to the lesson or substitutions for the ones already in the lesson. The first suggested lesson adjustment is for the activity worksheet. You can make the activity longer by creating, or having your students create, additional activity pages and holding several different rounds of competition. An optional addition to this lesson is to give your students index cards showing the different types of angles and have them use the cards to identify various right, obtuse, and acute angles in the classroom. You can also have them match their cards to angles outside, on a playground, or anywhere else you have access to. Finally, you can add an art project to this lesson by having students use a certain number of angles to create a piece of art, like a painting or picture.

Teacher Notes

The teacher notes page includes a paragraph with additional guidelines and things to think about as you begin to plan your lesson. It notes that this lesson revisits some things that your students may have already learned about, such as rays and endpoints. You can pair this lesson with other geometry lessons that relate to angles and angle types. This page also includes lines that you can use to add your own notes as you’re preparing for this lesson.


What is an Angle?

The Recognizing Angles lesson plan includes two pages on content. The lesson begins by listing some things that students see every day that have angles, like corners of rooms and edges of boxes. Students will learn that an angle is the space between two lines that share a common endpoint. Angles can be large or small. For example, the angle that forms between two fingers is smaller than the one between your arm at your elbow! Angles are a geometric shape that forms when two rays have a common endpoint. A ray, as students may already know, is a line with a start point but no end point. Rays can be short or long, but no matter what, they form an angle when joined at their endpoints. The lesson includes a few examples of rays that have formed angles by joining at their endpoints.

Next, students learn that we determine the different sizes of angles by the amount of space between two rays. We measure this space in degrees, represented by the degree symbol (°). Students will learn that these degrees are not the same things as the degrees we use to measure temperatures. We measure angles in math using the amount of space in a circle, which has a total of 360°.

The lesson shows a green circle broken into four right angles. Each of these right angles are 90°, so the total of all four is 360°. All right angles measure 90°. Acute angles measure less than 90° and obtuse angles measure greater than 90°. The lesson shows examples of each type of angle.

Angles can have any measurement larger than 0° and less than 360°. You can find angles everywhere once you know to look for them! We measure angles using a helpful tool called a protractor. We use these to find the exact number of degrees in an angle. Knowing how to identify angles and understanding how to measure them is an important skill. People who work in construction, architecture, art, design, and many other fields use them every day!

Key Terms

Here is a list of the vocabulary words students will learn in this lesson plan:

  • Angle: the space between two lines that share a common endpoint
  • Ray: a line with a start point but no end point
  • Right angles: angles with measurements of 90°
  • Acute angles: angles measuring less than 90°
  • Obtuse angles: angles measuring greater than 90°
  • Protractor: a tool used to find the exact number of degrees for an angle


The Recognizing Angles lesson plan includes three worksheets: an activity worksheet, a practice worksheet, and a homework assignment. You can refer to the guide on the classroom procedure page to determine when to hand out each worksheet.


Students work in pairs to complete the activity worksheet. The student pairs will compete with each other to see who can complete the activity the fastest. They will look at the activity worksheet and identify all of the right, acute, and obtuse angles. They will label right angles with an “R,” acute angles with an “A,” and obtuse angles with an “O.”

Students may also work either alone or in larger groups for this activity if you’d prefer.


The practice worksheet includes two exercises. For the first exercise, students will tell whether various statements about angles are true or false. For the second exercise, students will look at different letters and determine whether the shape of the letters include right, acute, obtuse angles, or no angle at all.


For the homework assignment, students will answer five questions about recognizing and measuring angles. They will also look at six different angles and determine if they’re acute, right, or obtuse.

Worksheet Answer Keys

This lesson plan includes answer keys for the activity worksheet, the practice worksheet, and the homework assignment. If you choose to administer the lesson pages to your students via PDF, you will need to save a new file that omits these pages. Otherwise, you can simply print out the applicable pages and keep these as reference for yourself when grading assignments.

Additional information


4th Grade



State Educational Standards


Lessons are aligned to meet the education objectives and goals of most states. For more information on your state objectives, contact your local Board of Education or Department of Education in your state.