GeometryConstructionsabout 3 minCCSS HSG.CO.D.12Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric software, etc.). Copying a segment; copying an angle; bisecting a segment; bisecting an angle; constructing perpendicular lines, including the perpendicular bisector of a line segment; and constructing a line parallel to a given line through a point not on the line.CCSS HSG.CO.A.1Know precise definitions of angle, circle, perpendicular line, parallel line, and line segment, based on the undefined notions of point, line, distance along a line, and distance around a circular arc.CCSS HSG.MG.A.3Apply geometric methods to solve design problems.+0
Roll a board on strange rollers, then spin a curved triangle in a square.
Lesson Plan
Follow a compass construction of the Reuleaux triangle, then explore curves of constant width.
Question: Ask what students spot and what they are curious about. Read “Does the board bump or ride flat?” aloud. Have each student guess and say why.
Question: Read “How much of the square does it carve?” aloud. Have partners explain their guesses to each other.
Big idea: Pause. Ask a student to say the idea in their own words.
Your turn: Have students try their own. Ask them to predict before they test.
How to run it
Whole classPut the lesson on the board. At each choice the class votes, then you select the winner.
SoloShare the link, QR code, or post to Google Classroom. Each student gets to take their own path.
