Know precise definitions of angle, circle, perpendicular line, parallel line High School | Students learn the exact definitions of basic geometric figures: what makes lines parallel or perpendicular, what a circle actually is, and how angles and line segments are precisely described. These definitions are the foundation for everything in geometry. | G.CO.A.1 |
Flexibly, efficiently High School | Transformations move, flip, or resize shapes on a grid. Students learn which ones keep a shape's size and angles intact, like sliding a triangle across the page, and which ones stretch or distort it. | G.CO.A.2 |
Given a rectangle, parallelogram, trapezoid High School | Students figure out which flips and turns map a shape exactly back onto itself. A square, for example, can be rotated a quarter turn or flipped across its center and look identical. | G.CO.A.3 |
Develop definitions of rotations, reflections High School | Rotations, reflections, and translations each have precise definitions built from angles, lines, and line segments. Students work out what makes each movement exact, not just a rough sketch of "flip" or "slide." | G.CO.A.4 |
Given a geometric figure and a rotation, reflection High School | Students draw a shape after sliding, flipping, or rotating it, then figure out the exact steps needed to move one shape onto another. | G.CO.A.5 |
Use geometric descriptions of rigid motions to transform figures and to predict… High School | Students slide, flip, or rotate shapes on a page and predict where each point will land. They also look at two shapes and decide if one can be moved onto the other perfectly, with no stretching allowed. | G.CO.B.6 |
Use the definition of congruence in terms of rigid motions to show that two… High School | Two triangles are congruent when their matching sides and angles are equal in measure. Students connect that idea to flips, slides, and turns, showing that if you can move one triangle exactly onto another, the sides and angles must match. | G.CO.B.7 |
Explain how the criteria for triangle congruence High School | Students explain why two triangles must be identical in size and shape when they share two angles and a side, two sides and an angle, or three sides. The reasoning connects back to flips, slides, and rotations. | G.CO.B.8 |
Flexibly, efficiently High School | Students prove geometric rules about how lines and angles relate, such as why vertical angles are always equal or why parallel lines cut by a third line create predictable angle pairs. | G.CO.C.9 |
Flexibly, efficiently High School | Students prove geometric facts about triangles, such as why the three interior angles always add up to 180 degrees and why the line connecting two sides at their midpoints runs parallel to the third side. | G.CO.C.10 |
Flexibly, efficiently High School | Students prove that opposite sides and angles of a parallelogram are equal, and that the diagonals bisect each other. The focus is on writing clear, complete geometric proofs, not just stating the facts. | G.CO.C.11 |
Make formal geometric constructions with a variety of tools and methods High School | Students use a compass and straightedge to construct precise geometric figures, like bisecting an angle or drawing a perpendicular line. The work is done by hand, following exact steps rather than estimating by eye. | G.CO.D.12 |
Construct an equilateral triangle, a square High School | Using only a compass and straightedge, students draw a triangle with equal sides, a square, and a six-sided figure that fit exactly inside a circle, with every corner touching the edge. | G.CO.D.13 |