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# Help on La Grange watch

1. What point on the sphere

is closest to the point ?

How do I find the condition of this to form a lagrange equation to solve this?

I have thought of this

and

Forming equation:

I don't know how to start it which is the original problem.

Finally learning Latex

2. (Original post by mathsRus)
What point on the sphere

is closest to the point ?

How do I find the condition of this to form a lagrange equation to solve this?

I have thought of this

and

Forming equation:

I don't know how to start it which is the original problem.

Finally learning Latex

You want to minimise the distance from the point to , not just minimise
This is the same as minimising the distance squared from to .
Then you simply need to add the constraint in and minimise.
3. (Original post by joostan)
You want to minimise the distance from the point to , not just minimise
This is the same as minimising the distance squared from to .
Then you simply need to add the constraint in and minimise.

So do I do
4. (Original post by mathsRus)

So do I do
Yes, that's what you want to minimise.
5. (Original post by ghostwalker)
Yes, that's what you want to minimise.
Thanks
6. some examples here too

http://www.thestudentroom.co.uk/show....php?t=3351861
7. totally off topic but are you good with perturbation theory? really need help.
8. (Original post by cooldudeman)
totally off topic but are you good with perturbation theory? really need help.
I have done some perturbation methods for solving non linear ODEs as a postgad but this is almost 30 years ago.
9. (Original post by TeeEm)
I have done some perturbation methods for solving non linear ODEs as a postgad but this is almost 30 years ago.
ok no worries

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