Slate industry in Spain keep cutting machinery cool. After quarrying regional authorities often dictate that the landscape is returned as much as possible to its original state, and waste rock left as part of the extraction process is returned adjacent to the quarry Slate industry in Spain 90% of Europes's natural slate used for roofing originates from the slate industry in Spain, with the region of Galicia being the primary source of production. Slate is a fine-grained metamorphic rock that splits into thin, smooth-surfaced layers. Metamorphic rock is rock which was once igneous or sedimentary and has been subsequently subjected to heat and pressure
Change of variables (PDE) can thus be visualized as rotation on torii. As a particular example, consider the simple harmonic oscillator, with formula_70 and formula_71, with Hamiltonian formula_72. This system can be rewritten as formula_73, formula_74, where formula_75 and formula_76 are the canonical polar coordinates: formula_77 and formula_78. See V. I. Arnold, `Mathematical Methods of Classical Mechanics', for more details. Change of variables (PDE) Often a partial differential equation can be reduced to a simpler form with a known solution by a suitable change of variables. The article discusses change of variable for PDEs below in two ways: For example, the following simplified form