CCSS.Math.Content.HSG-CO.D
The standard
Make geometric constructions
Common Core State Standards for Mathematics · High School — Geometry
What this standard means
Students need to use tools like a compass, straightedge, ruler, protractor, and geometry software to make accurate constructions. They should know common ones: copying a segment or angle, bisecting a segment or angle, making perpendicular and parallel lines, and constructing basic polygons.
Mastery looks like clean, repeatable steps with clear marks left on the page, not just a correct-looking picture. Students should be able to explain why the construction works using congruent circles, equal radii, or angle relationships. Common trouble spots are sloppy compass width, erasing guide arcs, and mixing up measuring with constructing.
Ways to teach it
- Have students construct a perpendicular bisector of a segment using only compass and straightedge, then test it by measuring distances to both endpoints.
- Ask students to write directions for copying an angle so clearly that a partner can follow them without seeing the original drawing.
- Give a half-sheet with three construction diagrams and ask students to label the next compass or straightedge move for each one.
- Connect constructions to carpentry by having students use perpendicular bisectors to locate the center of a circular tabletop drawing.
Plan a lesson for CCSS.Math.Content.HSG-CO.D
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Related standards
- CCSS.Math.Content.HSG-CO.C
Prove geometric theorems
- CCSS.Math.Content.HSG-CO.D.12
Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric ...
- CCSS.Math.Content.HSG-MG.A.3
Apply geometric methods to solve design problems (e.g., designing an object or structure to satisfy physical constraints or minimize cost; working with typograp...
- CCSS.Math.Content.HSG-MG.A
Apply geometric concepts in modeling situations