ā¦Levi wrote his first work, Sefer ha-mispar (āBook of the Numberā), dealing with arithmetical operations, including extraction of roots. In De sinibus, chordis et arcubus (1342; āOn Sines, Chords, and Arcsā) he presented an original derivation of the sine theorem for plane triangles and tables of sines calculated to fiveā¦
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