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,
Love triangle Love triangle A love triangle (also called a romantic love triangle or a romance triangle or an eternal triangle) is usually a romantic relationship involving three or more people. While it can refer to two people independently romantically linked with a third, it usually implies that each of the three people has some kind of relationship to the other two. The relationships can be friendships, romantic, or familial. The 1994 book "Beliefs, Reasoning, and Decision Making" states, "Although the romantic love triangle is formally identical to the friendship triad, as many have noted their actual implications are quite different...Romantic love