Informally explore angles as an attribute of two-dimensional figures. Identify and classify angles as acute, right, obtuse, straight or reflex.
Estimate angle measures. Using a protractor, measure angles in whole-number degrees and draw angles of specified measure in whole-number degrees. Demonstrate that angle measure is additive.
Solve perimeter and area mathematical and real-world problems, including problems with unknown sides, for rectangles with whole-number side lengths.
Solve problems involving rectangles with the same perimeter and different areas or with the same area and different perimeters.
Triangles can be classified by the angles that they contain, or the relationship between their side lengths. All triangles have two names: one name that describes their angles, and one name that describes their side lengths.
Classifying by Side Length
Classifying by Angle Measure
The tables below describe the triangle classificaton system.
Quadrilaterals are shapes that have 4 sides. Just like triangles, quadrilaterals can have multiple names. Some categories, like parallelograms, are broad. A parallelogram, for example, is any quadrilateral with two pairs of parallel sides. Rectangles, squares, and rhombuses are all parallelograms, for example. However, other categories are narrow. Squares, for instance, must have two pairs of parallel sides, four equal sides, and four right angles.
All rhombuses are parallelograms.
All rectangles are quadrilaterals and parallelograms.
All squares are quadrilaterals, parallelograms, rectangles, and rhombuses.