Person — Claudio Tolomeo. Featured in chapters 28 · 29 Linked atoms 4 linked atoms. 28 Circonferenza goniometrica e funzioni sin, cos, tan From chords to the sine, the story of a word Sine, cosine and tangent of an arbitrary angle 29 Formule di addizione, duplicazione, bisezione Ptolemy’s theorem and the chords of the Almagest The addition and subtraction formulae