Re: [微積] 偏微分微不出來...
※ 引述《Alcor (墨水藍)》之銘言：
: 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)
^^^^^^^^^^^^^^^^^^^^
這前面要有負號
: = -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)
∂[sin(x+y)+cos(x+y)]
--------------------- = cos(x+y) - sin(x+y)
∂y
∂e^(x-y)
--------- = -ye^(x-y)
∂y
∂[sin(x+y)+cos(x+y)]*e^(x-y)
-----------------------------
∂y
= [cos(x+y) - sin(x+y)]e^(x-y) - [sin(x+y) + cos(x+y)]e^(x-y)
= [cos(x+y) - sin(x+y) - sin(x+y) + cos(x+y)]e^(x-y)
= -2sin(x+y)*e^(x-y)
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 111.246.21.14
※ 編輯: MathforPhy 來自: 111.246.21.14 (11/12 17:20)
※ 編輯: MathforPhy 來自: 111.246.21.14 (11/12 20:38)
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