Angle trisection an angle of measure 30 degrees). It is possible to trisect an arbitrary angle by using tools other than straightedge and compass. For example, neusis construction, also known to ancient Greeks, involves simultaneous sliding and rotation of a marked straightedge, which cannot be achieved with the original tools. Other techniques were developed by mathematicians over the centuries. Because it is defined in simple terms, but complex to prove unsolvable, the problem of angle trisection is a frequent subject of pseudomathematical attempts at solution by naive enthusiasts. These "solutions" often involve mistaken interpretations of the rules, or are simply incorrect. Using
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