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
Type 90 Kyū-maru procurement plan was established in the 1980s while Japan was experiencing asset price bubble. After the asset price bubble burst in 1991 and the collapse of Soviet Union in 1992, Japan started to cut its defence budget. In order to save budget for Kongo Class missile destroyers and other new weapons, Japan made a plan to reduce the size of its tank force. The production of Type 90 therefore slowed down and part of its budget was shifted to the research and development of the new Type 10 main battle tank. Being 12 tonnes heavier than its predecessor Type 74