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,
1 in 60 rule is required, the numbers work out with the same rule: 1% over 1 NM ≈ 60' It is also useful to find out the lateral deviation from a given VOR course or radial: Each dot on a VOR indicator represents 2° of deviation, or 200' per dot per DME. There are other applications to this rule. One such application is time drift. An hour is equal to 60 minutes, and a minute is equal to 60 seconds, so some other relationships between angle and time can be observed. If a pilot is flying a leg of 120 miles and finds