# Clip 11/13: Standard 5: Use Appropriate Tools Strategically Using Quadrilaterals Part 2B

## Overview

Mathematically proficient students consider the available tools when solving a mathematical problem. These tools might include pencil and paper, [or] concrete models...

In this clip, Humphreys articulates the focus for day two of the group investigations of the properties of quadrilaterals: to prove that their conjectures are actually true. She shares examples of how students “kept track” of their own thinking, helping students in their meta-cognitive efforts at understanding how they’re thinking and how to document their understandings. The students mark a figure drawn from the given to help reason through the proof. This clip is also indicative of standard 6 (attend to precision).