Question

Is hessian the same as saddle point?

I have wrritten down in my notes the same formula both under the name Hessian and Saddle point. The formula is fxx * fyy - fxy

Answer 1

the hessian can be thought of as the second derivative

Answer 2

Ok i see that by the formula. You find fxx, fyy, fxy and plug into the formula. So what is the saddle point then?

Answer 3

um...

Answer 4

http://tutorial.math.lamar.edu/Classes/CalcIII/RelativeExtrema.aspx

Answer 5

D= fxxfyy-(fxy)^2<0 --> saddle point

Answer 6

so my question was are they the same. And by what you and zzrock said, they are the same thing correct? Same formula?

Answer 7

do you know what an inflection point is?

Answer 8

do you know how it relates to the second derivative?

Answer 9

this is similar to that

Answer 10

I don't I just learned about this on friday

Answer 11

I just wanted to know if that formula is the same for both , are they basically the same

Answer 12

Example of the Saddle point is where the function on the left is decreasing , while it on the right is increasing. So the function has no idea which its leading to if you look in many different pathways.

Answer 13

And the formula is not the same. Hessian has fxy^2, not just fxy as you said.

Answer 14

Sorry that is what I meant to put fxy^2

Answer 15

Hessian can yield 4 different types, it can be used to find local max, local min, saddle or useless info. so its probably not wise to make an assumption that hassian is equivalent to a saddle point.

Answer 16

ok. I may have been confused because my teacher does it differently than I saw it done on chegg

Answer 17

@Andysebb my assumption is that fxx is referring to the second partial derivative of f with respect to x? and the same goes for the other two? correct?