[微積分] 17.7 46題
好像很多人不會算
這題不要直接做太麻煩了
以下是jacobian的算法
set x=au y=bt z=cv
the the original ellipsoid can transfer to a sphere
2 2 2
u + y + z =1
我用p代表partail的符號
partial(x,y,z) | px/pu px/pt px/pv |
J = -------------------- = | py/pu py/pt py/pv |
partial(u,t,v) | pz/pu pz/pt pz/pv |
| a 0 0 |
= | 0 b 0 | = abc
| 0 0 c |
so ∫∫∫ dzdydx = ∫∫∫ |J|dudtdv
= ∫∫∫ abcdudtdv = abc ∫∫∫dudtdv
transfer to sphere coordinate
2π π 1 2
=abc ∫ ∫ ∫ r sinφdr dφdθ
0 0 0
it's obvious that the result of the integration is the volume of a sphere
which is 4π/3 so multiply by abc we have the volume of ellipsoid
4
= --- πabc
3
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