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(cos^2 10°-cos^2 80°)+sin^2 20°
人气:488 ℃ 时间:2020-02-06 09:15:00
解答
(cos^2 10°-cos^2 80°)²+sin^2 20°
=(cos^2 10°-sin^2 10°)²+sin^2 20°
=cos²20+sin²20°
=1
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