Saccheri–Legendre theorem Saccheri–Legendre theorem In absolute geometry, the Saccheri–Legendre theorem states that the sum of the angles in a triangle is at most 180°. Absolute geometry is the geometry obtained from assuming all the axioms that lead to Euclidean geometry with the exception of the axiom that is equivalent to the parallel postulate of Euclid. The theorem is named after Giovanni Girolamo Saccheri and Adrien-Marie Legendre. The existence of at least one triangle with angle sum of 180 degrees in absolute geometry implies Euclid's parallel postulate. Similarly, the existence of at least one triangle with angle sum of less than 180 degrees
Less-than sign is used to denote the beginning of a heredoc statement (where OUTPUT is an arbitrary named variable.) In Bash, «<word is used as a "here string", where word is expanded and supplied to the command on its standard input, similar to a heredoc. The less-than sign plus the equals sign (<=) is used for an approximation of the less-than-or-equal-to sign (≤). ASCII does not have a less-than-or-equal-to sign, but Unicode defines it at code point U+2264. In BASIC, Lisp-family languages, and C-family languages (including Java and C++), operator <= means "less than or equal to". In Sinclair BASIC it is