doing problem solving, including tasks in which properties of shapes are important components

using models and property lists, and discussing which properties are a necessary and sufficient condition for a specific shape

using informal, deductive language ("all," "some," "none," "if-then," "what if," etc.)

investigating certain relationships among quadrilaterals to establish if the converse is also valid (i.e., if a quadrilateral is a rectangle, it must have four right angles; if a quadrilateral has four right angles, must it also be a rectangle?)

using models and drawings as tools to look for generalizations and counter-examples

making and testing of hypotheses