Illustration of the horizontal coordinate system. The observer is
File:Right Angled Triangle in Assamese.svg - Wikimedia Commons
File:Triangle Sides ABC.svg - Wikipedia
Euler diagram of types of triangles, using the definition that
File:Triangle-law edit with 3 heights, acute.svg - Wikimedia Commons
File:Basic right triangle b.svg - Wikimedia Commons
File:Isosceles right triangle with legs length 1.svg - Wikipedia
File:Isosceles right triangle-01.svg - Wikimedia Commons
File:Angles in Triangles Example 5.svg - Wikibooks, open books for
File:Triangle.svg - Simple English Wikipedia, the free encyclopedia
File:Right triangle centroid.svg - Wikimedia Commons
File:Right triangle ABC.svg - Wikimedia Commons
Maslow and the biased pyramid - by Srikanth Ramanujam