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note that thinking "sinus" was used because of the curved "shape" is anachronistic |
further comment on etymology |
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==Etymology of Sine==
:''…the modern word "sine" comes from a mistranslation of the Hindu jiva.''
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::It was Robert of Chester's translation from the Arabic that resulted in our word "sine." The Hindus had given the name ''jiva'' to the half-chord in trigonometry, and the Arabs had taken this over as ''jiba''. In the Arabic language there is also the word ''jaib'' meaning "bay" or "inlet." When Robert of Chester came to translate the technical word ''jiba'', he seems to have confused this with the word ''jaib'' (perhaps because vowels were omitted); hence, he used the word ''sinus'', the Latin word for "bay" or "inlet." Sometimes the more specific phrase ''sinus rectus'', or "vertical sine," was used; hence, the phrase ''sinus versus'', or our "versed sine," was applied to the "sagitta," or the "sine turned on its side."
:(Note that the "versed sine" is 1–cos(&theta). I'm guessing that ''rectus'' and ''versus'' here refer to what we would now call the ''y'' and ''x'' coordinates, assuming that they originally drew a circle and measured the angle from the horizontal...Boyer doesn't say, however.) [[User:Stevenj|Steven G. Johnson]] 21:55, 25 Mar 2004 (UTC)
:By the way, assuming an etymology of ''sinus'' for sine because of the "curvaceous shape" of the sine (from the other meaning of ''sinus'' for curve, in particular the curved shape of a draped toga or garment) is probably an anachronism. Plots of the sine function ala analytic geometry didn't come until centuries after Chester. [[User:Stevenj|Steven G. Johnson]] 22:18, 25 Mar 2004 (UTC)
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