sin²10°+sin²20°+sin²30°+……+sin²80°+sin²90°=?
sin²10°+sin²20°+sin²30°+……+sin²80°+sin²90°=?
數(shù)學(xué)人氣：110 ℃時(shí)間：2020-06-17 11:36:43
優(yōu)質(zhì)解答
sin80=sin(90-10)=cos10sin²10+sin²80=sin²10+cos²10=1同理sin²20+sin²70=1sin²30+sin²60=1sin²40+sin²50=1sin²90°=1所以原式=5
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