Define and use the interior angle sum theorem for triangles.
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Students have experience working with triangles and angle measurements from seventh grade when they investigated unique triangles. While students may know that the angles in a triangle add up to 180°, in this lesson they have the chance to prove this fact using parallel line angle relationships.
If you need to adapt or shorten this lesson for remote learning, we suggest prioritizing Anchor Problem 1 (benefits from discussion) and Anchor Problem 2 (benefits from worked example). Find more guidance on adapting our math curriculum for remote learning here.
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Given that $${\overleftrightarrow{DE} \parallel \overleftrightarrow{AC}}$$ in the diagram below, prove that $${a+b+c=180}$$.
A Triangle's Interior Angles, accessed on Aug. 10, 2017, 9:48 a.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.
Modified by Fishtank Learning, Inc.In the picture below, lines $$l$$ and $$m$$ are parallel. The measure of $$\angle PAX$$ is $${31^{\circ}}$$, and the measure of $$\angle PBY$$ is $${54^{\circ}}$$.
What is the measure of $$\angle APB$$?
Find the Missing Angle, accessed on Oct. 13, 2017, 4:22 p.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.
Determine the angle measures of each interior angle in the triangle.
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The following resources include problems and activities aligned to the objective of the lesson that can be used to create your own problem set.
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In the diagram below, $${L_1 \parallel L_2}$$ and $${L_3 \parallel L_4}$$. Use the diagram to answer the questions that follow.
Grade 8 Mathematics > Module 2 > Topic C > Lesson 13 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..
Modified by Fishtank Learning, Inc.?