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 Post subject: Gradient Vector Check?Posted: Fri, 14 Oct 2011 12:12:26 UTC
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Joined: Thu, 13 Oct 2011 17:01:28 UTC
Posts: 16
So; I've trying to find the gradient vector at a general point (X,Y) in

(that's meant to be X to the power of three quarters, and Y to the power of a quarter)

I just want to check that my ordering and layout are correct for the answer, on the first line of my 2 by 1 vector I have

Beneath it, on the second line, I gain

I have to input X=15 and Y=50, I got an answer of 0.203. I just want to know if what I've done is correct, because I'm not too sure about my vector gradient, thanks

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 Post subject: Re: Gradient Vector Check?Posted: Fri, 14 Oct 2011 13:02:00 UTC
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Joined: Mon, 29 Dec 2008 17:49:32 UTC
Posts: 6007
Location: 127.0.0.1, ::1 (avatar courtesy of UDN)
nabran wrote:
So; I've trying to find the gradient vector at a general point (X,Y) in

(that's meant to be X to the power of three quarters, and Y to the power of a quarter)

I just want to check that my ordering and layout are correct for the answer, on the first line of my 2 by 1 vector I have

Beneath it, on the second line, I gain

I have to input X=15 and Y=50, I got an answer of 0.203. I just want to know if what I've done is correct, because I'm not too sure about my vector gradient, thanks

You mean or not --- note the braces. And similarly with your other lines.

So you should get
.

_________________

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 Post subject: Re: Gradient Vector Check?Posted: Fri, 14 Oct 2011 13:22:51 UTC
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Joined: Thu, 13 Oct 2011 17:01:28 UTC
Posts: 16
Yaaaay! Thank you; I won't make the mistake again now with my subscript, I can see how you did it! Sorry.

I'm glad I did something correct, so that means my next two parts of this question are correct.Also, I have two questions remaining on this question.

What does the first line in the vector actually mean? If I increase X by 1; the marginal product decreases by ^1/4 each time? I don't really get what this equation shows.

Also, how do you calculate the length of the gradient at the point (X=15, Y=50) in the second entry (Sorry, i got mixed up before, 0.203 refers to the second entry in the vector, not the first). There's not a topic about this in the book, is that simply 50^2-15^2? I'm thinking it can't be since it's a vector and it has more planes.

(I'm sure you'll be glad to know, once I understand this last part of the Q and complete the last part of the other Q which I'm trying now, I can start learning about 'Positive Definiteness' and so will be gone for a long time! - Hehe!)

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 Post subject: Re: Gradient Vector Check?Posted: Fri, 14 Oct 2011 19:29:05 UTC
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Joined: Thu, 13 Oct 2011 17:01:28 UTC
Posts: 16
Done it ^^ thank you!

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 Post subject: Re: Gradient Vector Check?Posted: Wed, 26 Oct 2011 23:08:24 UTC
 S.O.S. Newbie

Joined: Wed, 26 Oct 2011 23:05:31 UTC
Posts: 1
lol...u must be a student of Uni of Birm trying to do the problem sheet, rite?:P gotcha! lol

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