Special right triangle is 90°, leaving the remaining angle to be 30°. Right triangles whose sides are of integer lengths, with the sides collectively known as Pythagorean triples, possess angles that cannot all be rational numbers of degrees. (This follows from Niven's theorem.) They are most useful in that they may be easily remembered and any multiple of the sides produces the same relationship. Using Euclid's formula for generating Pythagorean triples, the sides must be in the ratio where "m" and "n" are any positive integers such that . There are several Pythagorean triples which are well-known, including those with sides in the
Hour angle is paired with the declination to fully specify the location of a point on the celestial sphere in the equatorial coordinate system. The local hour angle (LHA) of an object in the observer's sky is where LHA is the local hour angle of the object, LST is the local sidereal time, formula_3 is the object's right ascension, GST is Greenwich sidereal time and formula_4 is the observer's longitude (positive east from the prime meridian). These angles can be measured in time (24 hours to a circle) or in degrees (360 degrees to a circle)— one or the other, not both.