8011xx1
幼苗
共回答了24个问题采纳率：91.7% 举报
csc(x)/sin(x)-(cot(x)csc(x))/sec(x)
=1/sin²(x) - sin(x)/cos(x) * 1/sin(x) * cos(x)
=1/sin²(x) -1
=(1-sin²(x))/sin²(x)
=cos²(x)/sin²(x)
=cot²(x)
哪一步不明白,可以追问!
1年前
追问
8
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靳思
举报
第一步的cot(x)为什么会变成sin(x)/cos(x)呢? 公式的cot(x)=cos(x)/sin(x)?
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举报
8011xx1
写反了 csc(x)/sin(x)-(cot(x)csc(x))/sec(x) =1/sin²(x) - cos(x)/sin(x) * 1/sin(x) * cos(x) =1/sin²(x) - cos²(x)/sin²(x) =(1-cos²(x))/sin²(x) =sin²(x)/sin²(x) =1 这回对了 还有问题么？
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