Classifying Triangles Based on Properties of Angles

Les Willett's picture
Content Area(s):  
Grade Level(s):  
Oregon Common Core State Standards: 
Lesson Plan Details
45 minutes
Students will use Smartboard technology in an exploration of classification of two-dimensional shapes. Students will create and discuss rules for classification and then learn the classifications for triangles by angles.
Interactive SmartBoard with internet capability. Students slates. Protractors. Ability to stream internet or downloads of several websites.

Teacher will need to have several worksheets ready for class.  These include one containing many different shapes and sizes of two-dimensional shapes, another for recording individual and pair activities, and a classification worksheet to use for the exit activity.


The lesson will start with a Smart page showing many different sizes and shapes of two dimensional shapes. Students will be asked to sort these shapes and then compare their result with a partner. No rules were given on how to sort them. Several pairs of students will then be given the chance to show their strategies to the class by dragging the shapes into columns. The teacher will allow some time for discussion of the "rule" each pair used.  Students should discover some sort of rule about what is a polygon or the teacher will remind them of properties of polygons. Students will then be asked to resort their shapes into polygons and not polygons. Again a think-pair-share can be used with sharing between partners and within the whole group.

Next will come several pages discussing angles and measurement of angles. Included will be two interactive protractors that can be used to help give students an understanding of right angles, obtuse angles, and acute angles. One protractor has a hand that can be started and stopped and displays the angle measurement between where the hand started and where it stopped. The other can be dragged and rotated to allow the teacher or student to measure angles that all can see.  Among these pages is one where students can sing along to the angle the tune of BINGO.

Students will then get a page to practice sorting triangles into right, obtuse or acute categories. When each has had a chance to share with a partner the teacher will allow a class discussion.  When satisfied that the class is ready the teacher will hand out an exit task that asks students to sort several triangles into appropriate categories based upon angle properties.  


Teacher will spend time walking through the classroom and listening to student conversations. Teacher will have the opportunity to quickly assess students' knowledge during whole group sessions. The exit task will be a quick and easy to read assessment of each student at the end of the period.

Oregon Educational Technology Standards
Creativity and Innovation: 
1A. Apply existing knowledge to forecast possibilities and generate new ideas, products or processes.
Communication and Collaboration: 
2A. Interact and collaborate with peers, experts, or others employing a variety of digital environments and media.
Career Related Learning Standards
CR3B. Listen attentively and summarize key elements of verbal and non-verbal communication.
CR3C Give and receive feedback in a positive manner.