作者mk426375 (时雨)
看板trans_math
标题Re: [考古] 98东华
时间Sun Jun 12 18:19:49 2011
※ 引述《pp20624 (kk)》之铭言：
: 3.find the directional derivative of
: f(x,y) = sinx +e^xy
: at the point ( pi/2 , 0 ) in the direction of v =(1,1).
: 不知如何下手
: 有请大大帮忙 一题也很感谢
1
Let u = --- (1,1).
√2
fx(x,y) = cosx + ye^(xy), fx(pi/2,0) = 0
fy(x,y) = sinx + xe^(xy), fy(pi/2,0) = 1 + pi/2
π 1
D f(pi/2,0) = ( 0 , 1 + --- )‧--- ( 1 , 1 ) = ...
u 2 √2
--
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※ 编辑: mk426375 来自: 140.114.201.140 (06/12 18:21)