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 leading to higher per unit costs than comparable models from NATO countries such as the M1 Abrams and the Challenger 2. Development of upgrades to the Type 90 suffered both as a result of limited budget, which caused procurement delays, and funding prioritization in favor of the Type 10 Main Battle Tank. Due to a perception that Type 90s are unsuited to operations in the tight confines of Japan's urban areas, they are preferentially assigned to the JGSDF Fuji School Brigade and the 7th Armored Division based in Hokkaido, where there is sufficient room for maneuver. With the exception of