Triangle Inequality

This Triangle Inequality lesson plan also includes:

This STEM lesson plan presents a guided inquiry-based activity on exploring the relationship between the side lengths of a triangle. Class members are encouraged to also find the relationship between angle measure and side lengths. Notes, a pre- and post assessment, homework, and an exit ticket offer the teacher support in covering the concept.

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CCSS: Adaptable
Additional Tags

Instructional Ideas

  • Have the class determine an algebraic rule to quickly determine whether a triangle can be formed from any given side lengths
  • Spend as much time investigating the relationship between the side lengths and angle sizes as the side inequality relationship
Classroom Considerations

  • An extensive list of supplies is needed that includes uncooked spaghetti and/or straws
  • Student familiarity with collaborative group roles would be beneficial
  • This resource is only available on an unencrypted HTTP website. It should be fine for general use, but don’t use it to share any personally identifiable information

  • Data notes chart provided to assist with formative assessment
  • Pre-assessment is designed to determine prerequisite skills for the activity

  • The Hinge Theorem relationship is treated as an after-thought or only as an extension
  • Answers are not provided for the assessments
Common Core