# Intro: GeoGebra skills, terms, vocabulary & postulates

Author:
Zawierucha

The objectives of this activity: With the GeoGebra app: 1. you will become familiar with some of the tools used in GeoGebra. 2. you will explore what you can and can't change once you have constructed a figure. 3. You will work with 2 of the three undefined terms, point & line, in order to illustrate some postulates. With the follow-up questions: 1. You will review and extend your understanding of the postulates and definitions you encountered 2. You will review the vocabulary used in this activity. 3. You will use the Applet to make some observations and write some conclusions. What you should you do in your notebook: 1. Add any new vocabulary to your vocabulary section. 2. Write down questions and correct answers for any questions that you weren't sure about and/or got incorrect. 3. Keep track of new observations and facts that helps you extend your understanding of the material covered.

## Some of the questions will talk about congruence. Watch this short video before you answer the questions.

We encountered 2 postulates in this activity: 1. Through 2 points there is exactly one line 2. if two lines intersect, then they intersect in exactly one point. In your own words describe what each postulate is saying.

## 2. Definition

circle is all points in the same plane that lie at an equal distance from a center point. A radius of a circle is a segment whose endpts. are the center of the circle and a point on the circle. A diameter is a chord that contains the center of the circle. Define, chord (of a circle)

## 3. Definition

Define, ray.

In plane geometry we have three undefined terms one is "plane" ( a 2-dimensional surface that extends out indefinitely into space), what are the other two undefined terms mentioned in this activity.

## 5. Definition

Define, postulate.

Define, segment.

## 7. Explain

Explain why the following statement must be true: in a circle or in congruent circles, radii or diameters are congruent. (make sure to watch the video that explains congruent figures)

## 8. Fill-in

a. A circle has ________ radii and diameters. b. A segment has ________ midpoint(s). c. A line has ______ midpoint(s). possible answer choices: zero, one, two, three, infinite (unlimited)

Define, midpoint

## 10. Definition

Define, congruent (figures)

## 11. Vocabulary

﻿List all the vocabulary used in this activity.