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春芽
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cos(α-55)cos(α+5)+sin(α-55)sin(α+5)
=(cosacos55+sinasin55)(cosacos5-sinasin5)+(sinacos55-cosasin55)(sinacos5+cosasin5)
=(cosacos55+sinasin55)(cosasin55-sinacos55)+(sinacos55-cosasin55)(sinasin55+cosacos55)
=(cosacos55+sinasin55)(cosasin55-sinacos55+sinacos55-cosasin55)
=(cosacos55+sinasin55)*0
=0
1年前
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