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2013 Conference Proceedings - University of Nevada, Las Vegas

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Figure 2: The Structure <strong>of</strong> the LessonManifestations <strong>of</strong> Developing Student UnderstandingIn this lesson, the students collectively conjectured about the congruence <strong>of</strong> quadrilateralsusing four possibilities:1) Four sides and one angle: Side-Side-Side-Side-Angle (SSSSA)2) Three sides and two angles: Side-Angle-Side-Angle-Side (SASAS) and Side-Side-Side-Angle-Angle (SSSAA)3) Two sides and three angles: Side-Side-Angle-Angle-Angle, (SSAAA) and Side-Angle-Side-Angle-Angle-Angle (SASAA)4) One side and four angles: Side-Angle-Angle-Angle-Angle (SAAAA)Students then agreed that two quadrilaterals are congruent under SASAS, SSAAA, andSSSSA and proved these new theorems using common properties <strong>of</strong> triangle congruence (SSS,SAS, AAS). They also generated counter-examples to show when congruence <strong>of</strong> twoquadrilaterals cannot be established (for example, SASAA, or a rectangle and a square with twoequal sides). During the exploration <strong>of</strong> the criteria for the congruence <strong>of</strong> quadrilaterals, studentsalso explored possible cases regarding the positions <strong>of</strong> the angles and sides in quadrilaterals. The<strong>Proceedings</strong> <strong>of</strong> the 40 th Annual Meeting <strong>of</strong> the Research Council on Mathematics Learning <strong>2013</strong> 219

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