Prove the identity: cot²𝛳/(1+cot²𝛳)=cos²𝛳 and (1-tan²𝛳)/(1+tan²𝛳)=1-2sin²𝛳?
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2016-09-14 7:09 pm
收錄日期: 2021-04-21 21:52:15
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