In the previous post we talked about perpendicularity. Now, let’s talk about Similarity of Triangles, which are fundamental concepts in plane geometry, especially triangles. History of the similarity of triangles The optics used in entrance exams were discovered by Pierre Fermat in his work Variar Opera Mathematica of 1679. His original name is Clement Samuel Fermat, but he became known as Pierre Fermat. From Fermat’s studies we highlight two important results: