sin7°cos37°﹣sin83°cos53°的值为( ) A.﹣ B. C. D.
sin7°cos37°﹣sin83°cos53°的值为()A.﹣B.C.D.﹣...
sin7°cos37°﹣sin83°cos53°的值为( ) A.﹣ B. C. D.﹣
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sin7°cos37°﹣sin83°cos53° =cos83°cos37°﹣sin83°sin37° =cos(83°+37°) =cos120° =﹣  , 故选A. |
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