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Astronomer mathematical tool kit

This is the beginning of Giovanni Bianchini's Tabula magistralis quarta. The Tabule magistralis are a set of numerical tables belonging to an intermediate mathematical world. They are not astronomical because they do not directly tabulate astronomical quantities. They are not trigonometrical or mathematical either because they often depend on the value of some specific astronomical quantities like the obliquity of the ecliptic. Bianchini is the first Latin astronomer to publish a work devoted only to this kind of tables which probably were the building tools of many of his astronomical tables. He initiated in Europe a tradition of table making which will eventually end up about 150 years after with the creation of logarithm. The particular quantity tabulated here is what we call today the tangent function, of which this is also the first occurence in Europe. If all this was not enough this table, as all the other of the Tabule magistralis, is among the very first attestation of the use of decimal number and the decimal point. A fundamental mathematical innovation which must be linked to Giovanni Bianchini.