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2个回答
2010-10-10 · 知道合伙人教育行家
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展开全部
cos^2(π/12)-1/2
=[cos(2*π/12)+1]/2-1/2
=[cos(π/6)+1]/2-1/2
=[cos(π/6)]/2+1/2-1/2
=[(根号3)/2]/2
=(根号3)/4
=[cos(2*π/12)+1]/2-1/2
=[cos(π/6)+1]/2-1/2
=[cos(π/6)]/2+1/2-1/2
=[(根号3)/2]/2
=(根号3)/4
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