## Reflection: Connection to Prior Knowledge Introduction to Geometry - Section 5: Moving to Defined Terms, Line Segments and Rays

Every time I teach this lesson, I find that the students are fascinated by the topic of infinity. I love to ask about the number of points contained in a line, and the number of points contained in a line segment.  The students understand that the answer to both questions is infinity, but then I ask which infinity is bigger, and this question really throws them.  They have never thought about infinities having size, and they find this notion really intriguing.  In this case, I have learned that these two infinities are actually the same size, but there are, for example, many more irrational numbers than there are rational numbers, even though there are an infinite number of both.

Interestingly enough, there was recently an editorial in the New York Times that mentions the fact that infinity is one of the most fascinating topics in math.  The editorial is entitled How to Fall in Love with Math.

The Topic of Infinity
Connection to Prior Knowledge: The Topic of Infinity

# Introduction to Geometry

Unit 1: Tools of Geometry
Lesson 3 of 7

## Big Idea: There's no doubt about it - we've got to know them! Important geometric definitions and vocabulary.

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Standards:
Subject(s):
Math, point, Geometry, line, midpoint, line segment, congruent segments, plane, undefined terms, length, infinite, collinear, coplanar, intersecting, horizontal, vertical, ray, classroom norms and expectations
90 minutes

### Beth Menzie

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