Please refer to the following question : [HKAL 06II8]
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Pure Maths --- Integration
2008-02-29 3:58 am
回答 (1)
2008-02-29 4:11 am
✔ 最佳答案
The formula∫(0 to π) cosmxcosnx dx = 0
only holds when m≠n. When m=n, we have
∫(0 to π) cosmxcosnx dx
= ∫(0 to π) cos^2 nx dx
= ∫(0 to π) (1 cos2nx)/2 dx
= π/2.
Hence in the summation in the question, all terms are 0 EXCEPT the term when m=n.
That term is the L.H.S.
收錄日期: 2021-04-22 00:32:50
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080228000051KK02355