Proving Identity
2008-02-10 2:20 am
Given that [(tanx)/(sinz)-(tany)/(tanz)]^2=(tanx)^2-(tany)^2, prove that cosz=(tany)/(tanx)
回答 (1)
2008-02-10 2:33 am
✔ 最佳答案
[(tanx)/(sinz)-(tany)/(tanz)]^2=(tanx)^2-(tany)^2(tanx-tanycosz)^2/(1-(cosz)^2)=(tanx)^2-(tany)^2
rearrange the term,we have
-2tanxtanycosz=-(tany)^2-(tanxcosz)^2
(tanxcosz-tany)^2=0
cosz=tany/tanx
參考: me
收錄日期: 2021-04-22 00:16:06
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