# A first look at Euclid's Elements

## Instructions

#### Warning: Allow the Graphics and Java Applets to fully load before clicking anywhere

If you accidentally interupt the transmission before it is finished by clicking somewhere, you must press the "Refresh" button to start all over again from the beginning

Once you get to the main Page for Euclid's Elements follow the link called "Using the Geometry Applet" to get an idea how to move the objects and reset the diagram.

## The Questions YOU need to answer

1. You already know a lot of theorems. Identify what theorem or postulate you studied that go with the following propositions:

Book I, Prop 15
Book I, Prop 18
Book I, Prop 25
Book I, Prop 27
Book I, Prop 28
Book I, Prop 29
Book I, Prop 47

2. Go back to Book I, prop 15, and move the red dot. What relationship stays the same?

3. Can you make a side of a triangle so large that it is bigger than the other two combined? In your own words, justify your answer. Go to Book I, prop 20 (or prop 17) for ideas from Euclid).

4. What is a "rectilinear" angle? (go to Book I, prop 23)

5. Book I proposition 46 outlines instructions for constructing a square. Write a list of instructions so you can construct one with the same method with a compass and straight edge.