化简:1-sin6α(六次方)-cos6(六次方)α/1-sin4(四次方)α-cos4(四次方)α

问题描述:

化简:1-sin6α(六次方)-cos6(六次方)α/1-sin4(四次方)α-cos4(四次方)α
1个回答 分类:数学 2014-10-11

问题解答:

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(1-cos^6α-sin^6α)/(1-cos^4α-sin^4α)
1=sin^2α+cos^2α
原式=(sin^2α+cos^2α-cos^6α-sin^6α) /(sin^2α+cos^2α-cos^4α-sin^4α)
分母=sin^2α(1-sin^2α)+cos^2α(1-cos^2α)=2sin^2αcos^2α
分子=sin^2α(1-sin^4α)+cos^2α(1-cos^4α)
sin^2α(1-sin^4α)=sin^2α(1-sin^2α)(1+sin^2α)=sin^2αcos^2α(1+sin^2α)
同理cos^2α(1-cos^4α)=sin^2αcos^2α(1+cos^2α)
原式=sin^2αcos^2α(1+sin^2α+1+cos^2α)/2sin^2αcos^2α=3/2
 
 
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