As a special case, students practice identifying right angles and shapes with one or more right angles. Right angles have special significance, as they appear in several two dimensional figures like rectangles, square, right triangles etc. Recognizing right angles is also important for identifying perpendicular lines.

Common Core Alignment

4.G.2Classify 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.