Triangle Inequality Theorem

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Students will be able to determine if three side lengths can form a triangle.

Big Idea

Any three sides lengths can't form a triangle? NOPE! Students will use straws of various lengths to investigate this theorem.


10 minutes

OpenerAs students enter the room, they will immediately pick up and begin working on the opener – Instructional Strategy - Process for openers.  This method of working and going over the opener lends itself to allow students to construct viable arguments and critique the reasoning of others, which is mathematical practice 3

Learning Target:  After completion of the opener, I will address the day’s learning targets to the students.  For today’s lesson, the intended target is “I can determine whether three side lengths can form a triangle.” Students will jot the learning target down in their agendas (our version of a student planner, there is a place to write the learning target for every day). 

Summary + Homework

5 minutes

Instructional Strategy - Table DiscussionTo summarize this lesson, I am going to ask that students have a table discussion on the question – Think about the angles across from each side of a triangle – just knowing the side lengths, you can order the angles from largest to smallest – figure out how.  For this summary, I am going to have students discuss at their tables, and I am going to ask someone from each table to share out.  After every one shares, I will address the right/wrong answers.

Homework:  After the table discussion I will pass out the homework for the students to get started on. Eventhough the assignment is long, it should go quick!