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问题: 化简

(1-cos4/sin4)*[根号(1-cos^4)/sin2]

解答:

(1-cos4/sin4)*[根号(1-cos^4)/sin2]

(1-cos4/sin4)*[√(1-cos^4)/sin2]
=(1-cos4/sin4)*[√(sin^4)/sin2]
=(1-cos4/sin4)*[|sin4|/sin2]
因为π<4<2π,所以:sin4<0
=(1-cos4/sin4)*(-sin4/sin2)
=(cos4-1)/sin2
=[(1-2sin^2)-1]/sin2
=-2sin2