※ 引述《aacvbn (我是卑微的专科生)》之铭言： : ※ 引述《puppy110330 (慵懒的叶子)》之铭言： : : 1.find the directional derivative f(x,y,z)=xySinz in the direction : : --ˋ : : u =(1/2^1/2,-1,1/2^1/2) at the point(2,1,拍/6) : 1. : (sol) : -> -> -> : ▽f = ysin(z) i + xsin(z) j + xycos(z) k : π 1 : ▽f(2 , 1 , --- ) = < --- , 1 , 1 > : 6 2 : -> : π π u (3√2-4) : Ｄ_ -> f( 2 , 1 , --- ) = ▽f( 2 , 1 , ---- )‧------ = -------- : (v ) 6 6 ||->|| 4√2 : ||u || ------- ^ | 这代表?? ps:能否顺便解释题意?我不懂要求什麽>"<(2题都是)......麻烦了.... : : 2.find a triple interated integral for the volume inside the cone : : z^2=x^2+y^2 bounded by z=0 and z=8 --

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