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July 31, 2025, 08:43:01 am
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Author Topic: Dekoyl's Questions  (Read 14579 times)  Share 

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/0

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Re: Dekoyl's Questions
« Reply #45 on: March 24, 2009, 07:17:25 am »
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lol indeed :P
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dekoyl

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Re: Dekoyl's Questions
« Reply #46 on: April 01, 2009, 07:55:16 pm »
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By solving:

show that:


I don't really know what they want me to solve.
=\
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kamil9876

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Re: Dekoyl's Questions
« Reply #47 on: April 01, 2009, 08:15:41 pm »
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I'm not the best with matrices due too inexperience. But I remember that this is a proof of the formula for the inverse of a 2x2 matrix. So basically try to set up 4 simultaneous equations that involve the 8 variables. 8-4=4 so you should be able to find x in terms of only the variables in the first matrix... y in terms of only the variables in the first matrix... and so on. Once that is found, u know the second matrix but that second matrix is the inverse matrix since the product is the identity matrix.
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Voltaire: "There is an astonishing imagination even in the science of mathematics ... We repeat, there is far more imagination in the head of Archimedes than in that of Homer."

dekoyl

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Re: Dekoyl's Questions
« Reply #48 on: April 01, 2009, 08:19:40 pm »
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Quote from: kamil9876 on April 01, 2009, 08:15:41 pm
I'm not the best with matrices due too inexperience. But I remember that this is a proof of the formula for the inverse of a 2x2 matrix. So basically try to set up 4 simultaneous equations that involve the 8 variables. 8-4=4 so you should be able to find x in terms of only the variables in the first matrix... y in terms of only the variables in the first matrix... and so on. Once that is found, u know the second matrix but that second matrix is the inverse matrix since the product is the identity matrix.
Thanks Kamil! I'll try set those things up.
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dekoyl

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Re: Dekoyl's Questions
« Reply #49 on: April 02, 2009, 01:00:51 am »
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Sorries but I don't fully understand this property of a determinant.

- Replacing a row of a matrix by the sum of the row itself(huh?) and a scalar multiple of another row has no effect on the determinant.


Thanks :(
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/0

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Re: Dekoyl's Questions
« Reply #50 on: April 02, 2009, 01:01:44 am »
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If you have row A and row B, then you can replace row A with row , where k is a scalar.
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dekoyl

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Re: Dekoyl's Questions
« Reply #51 on: April 02, 2009, 01:03:25 am »
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Quote from: /0 on April 02, 2009, 01:01:44 am
If you have row A and row B, then you can replace row A with row , where k is a scalar.
Ah that's much more clear.

Thanks /0 =]
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dekoyl

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Re: Dekoyl's Questions
« Reply #52 on: May 05, 2009, 09:03:24 pm »
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Ressurection. =D

Q: How do we go about finding the surface normal of a non-flat surface (so vector normal) of a surface with equation ?

I first arranged it so I had the equation in the form then I'm not sure what to do :(

Thanks
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/0

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Re: Dekoyl's Questions
« Reply #53 on: May 05, 2009, 09:05:30 pm »
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What's ?
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dekoyl

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Re: Dekoyl's Questions
« Reply #54 on: May 05, 2009, 09:07:53 pm »
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Quote from: /0 on May 05, 2009, 09:05:30 pm
What's ?
Oh sorry :P

What I meant with was an equation that is in terms of x and y so maybe
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dekoyl

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Re: Dekoyl's Questions
« Reply #55 on: May 05, 2009, 09:31:52 pm »
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Wait is the vector normal to :
i jk?

Thanks
« Last Edit: May 05, 2009, 09:37:08 pm by dekoyl »
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Mao

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Re: Dekoyl's Questions
« Reply #56 on: May 05, 2009, 11:35:18 pm »
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yes. the gradient vector is perpendicular to the tangent vector, this can be shown with the chain rule. =]
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