(-sin²x-cosx-cos²x)/sin²x等于多少
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(-sin²x-cosx-cos²x)/sin²x=-(1+cosx)/ sin^2x=-2cos^2(x/2)/{4sin^2(x/2)* cos^2(x/2)}=1/2sin^2(x/2)
咨询记录 · 回答于2023-04-04
(-sin²x-cosx-cos²x)/sin²x等于多少
……
(-sin²x-cosx-cos²x)/sin²x=-(1+cosx)/ sin^2x=-2cos^2(x/2)/{4sin^2(x/2)* cos^2(x/2)}=1/2sin^2(x/2)
(-sin²x-cosx-cos²x)/sin²x=-(1+cosx)/ sin^2x=-2cos^2(x/2)/{4sin^2(x/2)* cos^2(x/2)}=-1/2sin^2(x/2)=-(1/2)*csc^2(x/2)
总之正确答案是-sin^2x-cos^2x=-1∵-(1+cosx)=-(1+2cos^2(x/2)-1)=-2cos^2(x/2)sinx=2sin(x/2) *cos(x/2 )1/ sin^2(x/2)= csc^2(x/2)∴(-sin²x-cosx-cos²x)/sin²x=(-1-cosx)/ sin^2x=-(1+cosx)/ sin^2x=-2cos^2(x/2)/{4sin^2(x/2)* cos^2(x/2)}=-1/{2sin^2(x/2)}=-(1/2)*csc^2(x/2)
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