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
180 Degrees South: Conquerors of the Useless "Chris Malloy's film strikes so deeply into the heart of Patagonia's wilderness we come to feel at home there". 180 Degrees South: Conquerors of the Useless 180 Degrees South: Conquerors of the Useless, or simply "180° South", is a 2010 documentary directed by Chris Malloy that covers the journey of Jeff Johnson as he travels from Ventura, California to Patagonia, Chile retracing the 1968 trip that Yvon Chouinard and Doug Tompkins took in their Ford E-Series Econoline Van. After finding footage of the 1968 expedition, Johnson decided to make climbing the Corcovado Volcano in Patagonia as his life goal and,