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Geometry Lesson on Angles for 3rd or 4th Grade
Objective:
The student will be able identify and draw acute, right, and obtuse angles.
Materials:
- chalk board
- chalk
- blank pieces of paper for each student
- one piece of bigger paper to fold
- post it notes
- blank paper for each group
- popsicle sticks with Velcro strips on the ends
- markers
- quiz
- homework sheet
Anticipatory Set:
Begin by drawing 3 polygons on the board and ask the class if they know of a word that describes all the shapes. The word
to be looking for is polygons. Tell the class that a polygon is a closed plane figure bounded by straight lines, and that
they can be measured by their angles. Point out that the angles of the polygon are where the straight lines meet. Pass out
a sheet of paper to each student and demonstrate to them to fold their paper in half and then in half again, to create a square.
Point out to the class that the corner of their paper created a right angle, which is measured at 90 degrees. Tell the class
that today they will be learning about angles and classify them as greater than, less than, or equal to a right angle.
Teaching:
-Begin by telling the students that there are three types of angles that are commonly used in geometry. These angles can
be seen in any polygon. They are acute, right, and obtuse. Continue by telling the class about these three types of angles
and drawing them on the board for the students to visualize.
-Right Angle: an angle that measures 90 degrees. Draw a right angle on the board. This will help students visualize the
angle and see that it measures 90 degrees. Remind them that the paper they folded is also a 90 degree angle. Take the corner
of the folded paper and put it against the angle, showing it is a right angle. Have them think of shapes that could have a
90 degree angle.
- Acute Angle: an angle that measures less than 90 degrees. Again, draw an acute angle on the board. Use the paper to
show that the angle is less than a right angle. Ask the class what shapes they know can have an acute angle.
- Obtuse Angle: first ask the class if they have any idea what an obtuse angle may be, based on what they already know.
Then tell them it is an angle that measures greater than 90 degrees. Draw one on the board for them to visualize. Again, use
the corner of the paper to show that it is less than a right angle. Ask the class what shapes can have an obtuse angle.
-After the class has been introduced to the three types of angles, ask them if there are any questions, if not, continue
on with the lesson. Go back to the polygons on the board. Based on what they know, ask the students if the angles of each
shape are acute, obtuse, or right angles. Be sure that there is at least one of each angle drawn on the board. Go over one
with the class, and then have a student come up and use a bigger piece of folded paper to show what type of angle the shape
has. Classify the angles of all the shapes.
-Erase the board and have three students come up to draw their own polygons on the board and have the class identify what
type of angles they have. They may use the folded paper if needed, but by this point, they should be able to visualize what
each angle looks like.
- Be sure everyone understands the three types of angles. If there are no questions, continue on with the lesson.
Guided Practice:
Have the class break up into groups of three. Tell them that together they will be creating and identifying angles. Give
each group the necessary supplies. They will need a post it notes, Popsicle sticks with Velcro pieces on them, to create the
angles, a blank piece of paper, a marker, and their folded piece of paper. Each group must use the Popsicle sticks to create
3 different angles; they may choose whatever angles they want. Next, they must draw three different polygons on their paper
that uses the three different angles. This is just what they did on the board as a class. Once each group has completed this,
this should take no more than 5 minutes; have each group move to the right to identify another groups angles. On the post
it note, write the name of the angle that is created by the Popsicle sticks and place it on the angle. Write the name of the
angles inside the shapes that were drawn on the paper. They may use their folded piece of paper to help them if needed. When
each group is done identifying the angles, they will go back to their own station and see if the group correctly identified
their angles. The teacher should walk around the room monitoring the students while this is being done. When everyone is done
collect all the supplies from each group
Closure:
Once everyone is back to their seats, hand out a short quiz to the class on the material they just learned. When they
are done with their quiz, they can bring it up to the teacher and pick up a homework sheet.
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