Triangle angle sum and exterior angle theorem

Teacher tools for this standard

Lesson Plan · Guided Notes · Exit Ticket · Re-teach · Homework

Lesson Plan →Objectives, pacing and practice, built from this lesson's brief.
Guided Notes →One page your students fill in and keep.
Exit Ticket →Three items at the end of class. No student accounts.
Re-teach →After an exit ticket: who missed what, and what to do tomorrow.
Homework →Assign practice; it grades itself.

SAT Description, and PSAT/NMSQT and PSAT 10 Description: "Know and directly apply relevant theorems such as the: • triangle angle sum theorem." PSAT 8/9 Description (the entire cell): "Know and directly apply the triangle angle sum theorem."

SAT Description, and PSAT/NMSQT and PSAT 10 Description: "Know and directly apply relevant theorems such as the: • triangle angle sum theorem."
PSAT 8/9 Description (the entire cell): "Know and directly apply the triangle angle sum theorem."

What you'll learn

State the triangle angle sum theorem (the three angles of any triangle sum to 180 degrees) and explain it using a line through one vertex parallel to the opposite side
Find a missing angle of a triangle from the other two, including the second acute angle of a right triangle (the two acute angles are complementary)
Use the angle sum to decide which angle combinations a triangle can have: at most one right or obtuse angle, and the right angle is the largest angle of a right triangle
Write and solve a linear equation from angle expressions in a triangle, and report the quantity the question asks for
Identify an exterior angle and its two remote interior angles, and apply the exterior angle theorem
Combine triangle angle facts with linear pairs, vertical angles, and parallel-line angle pairs in multi-step figures

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Slides

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