1. Find the right circular cylinder of maximun volume that can be inscribed in a
   sphere of radius 10 centimeters.

   請問這題如何算


                                                     →
2. Let f(x,y,z)=x+2xy-3z^2.Find the direction vector u  along which the
   directional derivative Duf at the point(1,0,4)reaches its maximum
   →
   u =
   第二題我算出來▽f(1,0,4)=(3,0,-24)

     →
  那 u 的答案是  1.(3,0,-24)
                 2.1/[(9+(-24))^1/2](3i,-24k)
                 3.(3/[(9+(-24))^1/2)],0,-24/[(9+(-24))^1/2])
  請問是用那個表示


以上請版友指導




※ 編輯: flygey          來自: 140.137.49.2         (07/03 13:59)
推 ht15trep:2. 他要的只有方向, 所以(3,0,-24)即可
→ ht15trep:1. 另為平面圓,極座標表高.半徑,求極值
→ ht15trep:1. 我算是2000π*[(√(2/3))^2]*√(1/3)