Slate industry in Spain 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 in varying degrees thereby altering its composition, structure and appearance. It is used extensively in the building industry, particularly for roofing tiles. The production of slate is estimated at 4 million tons per year. Galicia is situated on the
Polarization of an algebraic form "n" variables u = ("u", "u", ..., "u"). Suppose that "f" is homogeneous of degree "d", which means that Let u, u, ..., u be a collection of indeterminates with u = ("u", "u", ..., "u"), so that there are "dn" variables altogether. The polar form of "f" is a polynomial which is linear separately in each u (i.e., "F" is multilinear), symmetric in the u, and such that The polar form of "f" is given by the following construction In other words, "F" is a constant multiple of the coefficient of λ λ...λ in the expansion of "f"(λu +