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问题: 一道数学题

若sin(180+α)=1/√10,则[sec(-α)+sin(-α-90)]/[csc(540-α)-cos(-α-270)]=_______

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解答:

若sin(180+α)=1/√10,则[sec(-α)+sin(-α-90)]/[csc(540-α)-cos(-α-270)]=___

sin(180+α)=-sinα=1/√10
--->sinα=-1/√10--->cosα=±3/√10

 [sec(-α)+sin(-α-90)]/[csc(540-α)-cos(-α-270)]
= [secα-cosα]/[cscα-sinα]
= [sinα(1-cos²α)]/[cosα(1-sin²α]
= sin³α/cos³α
= ±1/27