Q.

Who was the first to use the expressions sine and cosine, defining them as lengths,rather than the ratios we know them as today ?

Asked by khabardar,
20 Apr '12 07:08 pm

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1.

Another of the Baghdad astronomer-mathematicians was al-Battani, and his notable achievements were, first, that he gave up the old Greek system of chords of angles and adopted the far more convenient trigonometrical proportion known as the sine; he also used its converse ratio, the cosine. With Hipparchos and Ptolemy the Greeks had come close to trigonometry but they had never finally settled on the ratios that al-Battani adopted, and which, because of their simplicity and convenience, were to revolutionise the mathematics of triangles used so much in astronomy and surveying, divesting it of some of its previous difficulty. Al-Battani's second achievement was his use of trigonometry, and the projection of figures from a sphere on to a plane, to allow him to get some new and elegant solutions to astronomical problems. Al-Battani (850-929 CE) being the first to use the expressions "sine" and "cosine" and was very much aware of the superiority of his `sines' over the Greek chords [19]. Hi
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Answered by anil garg, 18 May '12 02:00 am
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Al-Battani was the first to use the expressions sine and cosine, defining them as lengths,rather than the ratios we know them as today

- Hitti, P.K. (1970), History of the Arabs, tenth edition, Mac Millan St Martin's Press, p. 572.

- Nallino C.A, (1944), Raccolta di scritti Editi e Inediti, Roma.

- Hitti, P.K. (1970), History of the Arabs, tenth edition, Mac Millan St Martin's Press, p. 572.

- Nallino C.A, (1944), Raccolta di scritti Editi e Inediti, Roma.

Source: http://www.1001inventions.com/academicreferences

Answered by hazir jawab, 20 Apr '12 07:12 pm
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