An illustration from Oliver Byrne’s 1847 edition of Euclid’s Elements. Euclid’s fourth postulate states that all the right angles in this diagram are congruent. Image: Public domain, via Wikimedia Commons.
Why the heck do we need a postulate that says that all right angles are equal to one another? You probably remember lear [...]
Posts tagged euclidean geometry
What’s the Deal with EuclidR...
An illustration from Oliver Byrne’s 1847 edition of Euclid’s Elements. Euclid’s fourth postulate states that all the right angles in this diagram are congruent. Image: Public domain, via Wikimedia Commons.
Why the heck do we need a postulate that says that all right angles are equal to one another? You probably remember lear [...]
The Math Wars, Lewis Carroll Style
Lewis Carroll in 1863, photographed by Oscar Gustave Rejlander. Image: Public domain, via Wikimedia Commons.
Carroll’s book was a salvo in the “math wars” of the day, the subject of which was how best to teach geometry. Euclid was the standard textbook in private schools that taught mathematics, but many people found it wanting. To them, it w [...]
Chasing the Parallel Postulate
If you’d like to see these again, you’d better accept the parallel postulate. Image: Webber, via Wikimedia Commons.
Euclidean geometry, codified around 300 BCE by Euclid of Alexandria in one of the most influential textbooks in history, is based on 23 definitions, 5 postulates, and 5 axioms, or “common notions.” But as [...]
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