# Euclid's Elements - Books 1-4 (samples)

This collection features several apps that were created for the electronic book for the iPad that adds interactive diagrams to Euclid’s Elements, a mathematical classic (Available from the iTunes store).

Tags: Euclid, Elements, Geometry, Proposition, Proof

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#### Collection Contents:

##### Euclids Elements - Book 1 - Proposition 01
The very first proposition, in which Euclid creates a equilateral triangle from a straight line by using two circles.
##### Euclids Elements – Book 1 – Proposition 22
This app shows how to create a triangle when you’re given a line composed of lines A, B, and C.

Tags: Euclid, Elements, Geometry

##### Euclids Elements – Book 1 – Proposition 42
To construct, in a given rectilineal angle, a parallelogram equal to a given triangle. In other words, given angle D and triangle ABC (in blue), construct a parallelogram (in yellow) that has an equal area to triangle ABC.
##### Euclids Elements - Book 1 - Proposition 45
Creating a parallelogram equal to a given quadrilateral with a given angle.
##### Euclids Elements – Book 1 – Proposition 47
The famous Pythagorean Theorem. Can you see how it works?
##### Euclids Elements - Book 2 - Proposition 14
One of my favorite apps because it looks deceptively simple, but takes some really creative thinking. This app creates a square (in red) that has the same area as a given quadrilateral.
##### Euclids Elements – Book 3 – Proposition 08
This proposition proves that line AD is longest, ED is shorter, FD is shorter than ED, and CD is even shorter.and that for any line there is only one other line with a point on the circle and a point at D that is equal. (Unless you drag it to somewhere it's not supposed to be) I like it because it’s colorful.

Tags: Euclid, Elements, Geometry, Triangle

##### Euclids Elements - Book 3 - Proposition 14
Creating a tangent on a circle given point A that is outside the circle.

Tags: Euclid, Elements, Geometry, Circle, Tangent

##### Euclids Elements - Book 4 - Proposition 15
Skipping straight ahead to book 4 (shh this one is actually a first draft) Although GeometryExpressions allows you to create polygons with anywhere from 3 to 100 sides, Euclid gives us a way to create a regular hexagon that doesn't need such fancy technology.
##### Euclids Elements – Book 4 – Proposition 11
Can you create a regular pentagon without a protractor? Because it’s pretty impressive how Euclid did it with only a compass and a ruler. Note that the yellow triangle is similar to the one inside the pentagon.