Lesson Plan

Classify two-dimensional figures based on the presence or absence of parallel lines (e.g., parallelogram has two pairs, trapezoid has exactly one pair, triangle has none)

Classify two-dimensional figures based on the presence or absence of perpendicular lines (e.g., rectangle has four pairs of perpendicular adjacent sides, rhombus may or may not)

Classify two-dimensional figures based on the presence or absence of angles of a specified size (right, acute, obtuse)

Recognize right triangles as a category and identify right triangles among a set of triangles

Use the properties of parallel lines, perpendicular lines, and angle types as the basis for classification -- not just the shape's name

4.G.A.2

4.G.A.2: Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or the presence or absence of angles of a specified size. Recognize right triangles as a category, and identify right triangles.