# Clip 27/29: Standard 1: Making Sense and Perseverance Using Quadrilaterals Part 2B

## Overview

*Mathematically proficient students start by explaining to themselves the meaning of a problem and looking for entry points to its solution... They make conjectures about the form and meaning of the solution and plan a solution pathway rather than simply jumping into a solution attempt.*

On the second day of Humphreysâ€™ exploration of the properties of quadrilaterals, students work through their understandings of congruent triangles, the triangle postulates, parallel lines, transversals, and other geometric properties to apply those to create proofs for the quadrilaterals. Humphreys illustrates how to use selected notation in a proof as students work through the logic and reasoning. This clip is also indicative of standard 3 (construct viable arguments and critique the reasoning of others) and standard 6 (attend to precision).