# I have two question.

1. Oct 21, 2007

### MarianaA

Hi every one, I have two questions, I hope some one can help me.
Thanks.

How can I distinguish between a maximum, minimum or a saddle?

When are times when a particular coordinate system is a better choice the n the other two (rectangular, cylindrical and spherical)?

2. Oct 21, 2007

### EnumaElish

You could start by writing out the definition for each.

3. Oct 21, 2007

### MarianaA

but I dont know the definition

4. Oct 21, 2007

A minimum occurs when the Hessian is positive definite, a maximum when it is negative definite, and a saddle point when the Hessian has positive and negative eigenvalues.

5. Oct 21, 2007

### MarianaA

Thanks ^_^

When are times when a particular coordinate system is a better choice the n the other two (rectangular, cylindrical and spherical)?

6. Oct 21, 2007

### EnumaElish

7. Oct 21, 2007

### EnumaElish

I am assuming this is not homework. If it is, this thread will probably be deleted.

8. Oct 21, 2007

### MarianaA

Well I need to know this so I can do my homework
Thanks ^_^