Euclidean geometry equal (SAS), or two angles and a side equal (ASA) (Book I, propositions 4, 8, and 26). Triangles with three equal angles (AAA) are similar, but not necessarily congruent. Also, triangles with two equal sides and an adjacent angle are not necessarily equal or congruent. The sum of the angles of a triangle is equal to a straight angle (180 degrees). This causes an equilateral triangle to have three interior angles of 60 degrees. Also, it causes every triangle to have at least two acute angles and up to one obtuse or right angle. The celebrated Pythagorean theorem (book I,
Triangle and Robert Triangle and Robert Triangle and Robert is a webcomic by Patrick Shaughnessy that ran from August 1999 to September 2007. It is about the adventures of two polygons, an equilateral triangle named 'Triangle', and a rhombus named 'Robert'. As Patrick Shaughnessy, appearing in the strip as 'the Cartoonist', has explained on many occasions, he can't draw, and he makes up the story as he goes along. All of the characters are simple shapes that he creates using a cheap paint program. More complicated objects are represented by simpler stand-ins (a sheep, for instance, appears as a rectangular placeholder marked "Insert