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#1 2006-05-14 01:38:14

renjer
Member
Registered: 2006-04-29
Posts: 50

Lagrange

Use Lagrange multipliers to find the minimum distance from the point (5,5,4) to the paraboloid z=4-x^2-y^2.

I know a lot about Lagrange multipliers, they're quite easy, but the problem is, how do you find the distance from a point in space to a surface?

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#2 2006-05-14 02:20:25

Jai Ganesh
Administrator
Registered: 2005-06-28
Posts: 45,969

Re: Lagrange

I don't know about Lagrange multipliers and read about it here.

If your problem requires finding the distance between a point and a surface, the distance required must be the shortest distance to the point from normal to the surface!


It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#3 2006-05-15 00:41:20

renjer
Member
Registered: 2006-04-29
Posts: 50

Re: Lagrange

Then how can I relate that to Lagrange multipliers? I know there is supposed to be 2 equations f(x,y,z) and g(x,y,z) but now I don't know which two equations can I use.

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#4 2006-05-15 02:37:32

George,Y
Member
Registered: 2006-03-12
Posts: 1,379

Re: Lagrange

you can set up a distance function,
maximize it or its square under the constraint z=4-x^2-y^2.


X'(y-Xβ)=0

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