Lesson plan

Find unknown angles by using angle properties

teaches Common Core State Standards CCSS.Math.Content.4.MD.C.7 http://corestandards.org/Math/Content/4/MD/C/7
teaches Common Core State Standards CCSS.Math.Practice.MP1 http://corestandards.org/Math/Practice/MP1
teaches Common Core State Standards CCSS.Math.Practice.MP7 http://corestandards.org/Math/Practice/MP7

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Big Ideas: Angle properties can help you find missing angles in a figure. Equations are a way to express how to solve for a missing angle. This lesson builds on students' knowledge of benchmark angles and decomposing/composing angles. The task asks students to examine pieces of a stained glass window and determine three angle measures without a protractor. Through examining the benchmark angles (90°, 180°, 360°), students will see that those angle properties assist in finding unknown pieces, leading students to a deeper understanding that angles are additive. Students are asked to write an equation to help solve for the unknown angle measure. Their work in writing equations builds towards students' future work in solving algebraic expressions with variables. Vocabulary: benchmark angles, decompose, equation Special Materials: none