[微積] 偏微分微不出來...

[Alcor (墨水藍)]

        題目是 [sin(x+y)+cos(x+y)]*e^(x-y)

        求對 y 做偏微分

        我的算法是

        {[cos(x+y)+sin(x+y)]+[-sin(x+y)+cos(x+y)]}*-e^(x-y)

        = -2cos(x+y)*e^(x-y)

        請問是哪裡出差錯了 Q_Q

        補充 答案是給 -2sin(x+y)*e^(x-y)

--

        全部舊記憶 這刻重遊

                http://www.wretch.cc/blog/montent

                        By:墨水藍

--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 114.33.74.196
→ harveyhs    :對y偏微有-1啊
→ Alcor       :可是把對y篇微的-1修正 答案還是不對也...
※ 編輯: Alcor           來自: 114.33.74.196        (11/12 16:02)
→ APM99       :你的微分方法是什麼阿
→ APM99       : f(y) =  [sin(x+y)+cos(x+y)]  ; g(y)=e^(x-y)
→ APM99       :f'(y)g(y)+g'(y)f(y) =
→ kittor      :sin(x+y)有消掉嗎
→ Sumboy      :你提出-1了所以後面應為[sin(x+y)-cos(x+y)]吧?
→ kittor      :-2[sin(x+y)+cos(x+y)]*e^(x-y)