Geometry Lesson Seven:

Acute and Obtuse Angles

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Objective:. Students will demonstrate an understanding of right, acute and obtuse angle triangles by constructing angles with pipe cleaners and examining angles on pattern blocks.

Grade: Three/ Four

Length of Lesson: 1 hour

GCO: Students will demonstrate spatial sense and apply geometric concepts, properties, and relationships.

Related SCOs:

·        4E6: recognise, name, describe, and construct acute and obtuse triangles

Materials:

·        Pattern blocks  

·        Pipe Cleaners

Procedure:

·        Have the students find right angles on the objects in the room.  

·        The students will make right angles with pipe cleaners.
Many of the students will have made angles that have equal arms.  Ask the class if an angle must have equal arms.

·        Draw a right angle on the board.  Point out that the angle is a quarter turn regardless of the length of the arms.  

·        Draw an acute angle and ask the students how it compares to a right angle.
Introduce the term acute angle as being an angle less than a right angle.

·        Ask the students to create acute angles with pipe cleaners reminding them that the sizes of the arms of the angle are not important. 

·        Draw an obtuse angle on the board and ask the student if the angle is acute.

·        Ask the students if the angle is right. How would it compare to a right angle?

·        Introduce the term obtuse angle as being an angle greater than a right angle. 

·        The students will create obtuse angles with pipe cleaners. 

·        In groups of 2 or 3, the students will look for acute, right, and obtuse angles on the sides of the pattern blocks.  

Evaluation: The teacher can determine the level of student understanding by looking at the triangle models they have made and by listening to the answers to the questions posed in class. The teacher should move around the classroom and ask students questions to determine their progress, such as, what type of angle is being produced by the hands on the clock on the wall.

Extension: Students can classify the different angles (acute, obtuse and right) produced by the different lengths.

Inclusion Strategies:

Hearing Impaired: Visual aids will be used for those students who are hearing impaired and handouts will be given with instructions for the lesson. The hearing impaired student will be paired with a non-hearing impaired classmate and class discussion points will be written on the chalkboard for all students to see.  

Visually impaired:  Visually impaired students will be paired with a student who is not visually impaired.  These students will be given the instructions orally.  These students will be able to know what is going on in the class discussions through hearing. Their partner can help them find objects in the room and determine the size of the angle by describing it. The visually impaired student will be able to feel the objects and try on his/her own to determine if the angle is right, acute or obtuse. The visually impaired student will also be provided with models of the shapes in question so that they can feel the shape and make judgments about the properties that they feel.

Students of English as a second language:  Students where English is a second language should be provided with lots of visual support, as with students with hearing impairment.