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(cos(π/8))^4-(sin(π/8))^4
人气:296 ℃ 时间:2020-04-08 09:05:34
解答
(cosπ/8)^4-(sinπ/8)^4
=[(cosπ/8)^2+(sinπ/8)^2][(cosπ/8)^2-(sinπ/8)^2]
=1*(cosπ/4)
=cos45°
=(根号2)/2
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