Interior Angles of a Triangle

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Students will apply their knowledge of angle relationships to set up and solve equations to find missing values in a triangle.

Big Idea

Equations and geometry - a match made in heaven!


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 set up equations using angle relationships in order to solve for missing values."


45 minutes

Guided Notes: This lesson will begin with very basic notes on the sum of the interior angles of a triangle.  Most students already know that the sum of the angles is 180, but I want to revisit that fact before moving forward with class.  I will ask for student input on what they think we should do if we know that the interior angles sum to 180, and we have angle measures and expressions for each angle.  I am hoping that they will be able to set up an equation based on what we did in the previous lesson. After working a couple of problems together, I will have the students work in their table groups to finish the practice and then go to the board to share their work.

Versatiles Activity: For the remainder of class students will work in their table groups to solve a mix of 12 problems that cover all angle relationships that we have studied.  I will use this time to pull a small group together for extra assistance as needed.