Right angle of what a right angle is, namely two straight lines intersecting to form two equal and adjacent angles. The straight lines which form right angles are called perpendicular. Euclid uses right angles in definitions 11 and 12 to define acute angles (those smaller than a right angle) and obtuse angles (those greater than a right angle). Two angles are called complementary if their sum is a right angle. Book 1 Postulate 4 states that all right angles are equal, which allows Euclid to use a right angle as a unit to measure other angles with. Euclid's commentator Proclus gave a
900 Degrees 900 Degrees "900 Degrees" is a song by German DJ and producer Ian Pooley. The song was released as a single from his sixth studio album, "Since Then", released in October 2001. Upon its release, the song peaked within the top 60 on the UK Singles chart and remained Pooley's highest-peaking UK single for more than a year, until his 2002 single "Piha" peaked higher. The song also entered the "Billboard" Hot Dance Breakouts Maxi-Single Sales chart, becoming his first chart entry there. "900 Degrees" samples two other songs: "Make That Move," a 1980 soul/funk song recorded by Shalamar; and