There are 13 books in Euclid's Elements.
'Elements' was written by Euclid.
The thirteenth book in Euclids Elements has no specific title, but covers the Pythagorean proofs of Theaetetus (c. 417-369 bc) and the construction of the five regular Platonic solids (pyramid, cube, octahedron, dodecahedron, icosahedron) inside a given sphere.
need a simple explanation of Euclids theory.
His mathematical books called Elements. His work on geometry, particularly his famous axioms.
The Elements which are 13 volumes