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圖片參考：http://r140.n100.queensu.ca:8081/wwtmp/equations/11/4c7eaf1a15e02ee34677ea120e7a891.png
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derivative
2011-11-24 1:14 pm
回答 (1)
2011-11-24 5:15 pm
✔ 最佳答案
f(x)=2Cos(2lnx))，find f’(x)，f”(x) Sol
f’(x)=df(x)/dx
=d[2Cos(2lnx)]/dx
=d[2Cos(2lnx)]/d(2lnx)]*[d(2lnx)/dlnx]*[dlnx/dx]
=－2Sin(2lnx)*2*(1/x)
=－4Sin(2lnx)/x
xf’(x)=－4Sin(2lnx)
xf”(x)+f’(x)
=d[－4Sin(2lnx)]/d(2lnx)]*[d(2lnx)/dlnx]*[dlnx/dx]
=－4Cos(2lnx)*2*1/x
=－8Cos(2lnx)/x
xf”(x)－4Sin(2lnx)/x=－8Cos(2lnx)/x
xf”(x)=[4Sin(2lnx)－8Cos(2lnx)]/x
f”(x)=[4Sin(2lnx)－8Cos(2lnx)]/x^2
收錄日期: 2021-05-02 12:05:34
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20111124000051KK00116