Less-than sign been repurposed for a range of uses and operations. The less-than sign (<) is an original ASCII character (hex 3C, decimal 60). The less-than sign is used for an approximation of the opening angle bracket (⟨). ASCII does not have angle brackets. In BASIC, Lisp-family languages, and C-family languages (including Java and C++), operator < means "less than". In Coldfusion, operator .lt. means "less than". In Fortran, operator .LT. means "less than"; later versions allow <. In Bourne shell, operator -lt means "less than". The double less-than sign («) is used for an approximation of the much-less-than sign (≪) or
Space (mathematics) projective geometry nor defined from the notions mentioned there. The question "what is the sum of the three angles of a triangle" is meaningful in Euclidean geometry but meaningless in projective geometry. A different situation appeared in the 19th century: in some geometries the sum of the three angles of a triangle is well-defined but different from the classical value (180 degrees). Non-Euclidean hyperbolic geometry, introduced by Nikolai Lobachevsky in 1829 and János Bolyai in 1832 (and Carl Friedrich Gauss in 1816, unpublished) stated that the sum depends on the triangle and is always less than 180 degrees. Eugenio Beltrami