Math Terms - Visually Described ?

SuperLynx · 2011-01-19 15:36:23

First on to my Matrix question, that I posted then onto my Array question I'm not using Matlab but as you may or may not have remembered the 3D program I use had a similar way to create complex effects which is what I'm trying to learn

I won't reply until tomorrow as it's almost 11 PM, I just wanted to get my question posted

bobbym · 2011-01-19 15:44:14

Okay will see you tomorrow then.

SuperLynx · 2011-01-20 00:54:21

I don't understand with Matrices there is a A,B,T,C before the brackets. Then within the brackets there is usually a big letter with two smaller letters as in S(y,z). I remember you telling me they are variables but whenever I see a matrix math question there adding or multiplying these together how is that possible do you have to treat them as numbers ? How are they knowing what A*B is ? To get an exact idea of what I mean see this page:

http://www.analyzemath.com/Calculators/determinant_3by3.html
This brings me to another Sub-Question how do you calculate Determinant?

Arrays, what are some terms like indexInArray ? I know that an Array is a list, and that is all I know

Last edited by SuperLynx (2011-01-20 00:58:29)

bobbym · 2011-01-20 05:39:05

Hi SuperLynx;

I don't understand with Matrices there is a A,B,T,C before the brackets.

The names that are given to a matrix are capital letters like A,B etc.

The matrix A above is a 3x3 matrix.

How are they knowing what A*B is ?

Please be careful with your choice of letters. In math we use capitals for matrices. x,y,z etc for variables. In answer to the question the rules of algebra apply to numbers and variables. You do not know what A*B is specifically. What it is saying is when you take 2 matrices ( any two matrices ) and you multiply them then something will happen.

That site provides a java applet for computing the determinant of a 3x3.

Now the A matrix has variables for elements. What that is saying is each variable can be any number.

SuperLynx · 2011-01-20 12:08:14

Before I reply how do I quote your matrices ?

bobbym · 2011-01-20 12:16:19

Put them between the quote tags:

quote and \quote with bracket around them.

SuperLynx · 2011-01-20 12:43:21

I can't add the graphic in the quote do I have to upload it again ?

bobbym · 2011-01-20 14:23:43

Is it on your hard drive or on a site?

SuperLynx · 2011-01-20 16:09:02

The matrix graph you posted in post #229

bobbym · 2011-01-20 16:14:29

Just click it and the latex code for it will come up. Then put that between the math tags.

SuperLynx · 2011-01-21 03:05:32

Just click it and the latex code for it will come up. Then put that between the math tags.

That is what I meant, now onto my questions

The A has not meaning it is just a variable for something ?

Please be careful with your choice of letters. In math we use capitals for matrices. x,y,z etc for variables. In answer to the question the rules of algebra apply to numbers and variables. You do not know what A*B is specifically. What it is saying is when you take 2 matrices ( any two matrices ) and you multiply them then something will happen.
That site provides a java applet for computing the determinant of a 3x3.

If a matrix is written as such:

That you just substitute the letters with numbers ? How come when I see some matrices online they are doing the math with letters, doesn't make sense to me. The java applet that can find out the determinant I don't understand how that is figuring it out ? I wish I could understand how to write in latex so I can write things out so it could be understood easier, as in writing out arrays etc.

Last edited by SuperLynx (2011-01-21 03:06:24)

bobbym · 2011-01-21 03:22:24

Hi;

A is that matrix now. Whenever you refer to that matrix you would say A and vice versa.

How come when I see some matrices online they are doing the math with letters, doesn't make sense to me.

It will but it will take time.

The java applet that can find out the determinant I don't understand how that is figuring it out ?

It is just using a formula and a technique called plugging in. Nothing amazing about it.

To learn latex you start here:

http://www.mathisfunforum.com/viewtopic.php?id=4397

SuperLynx · 2011-01-21 04:06:46

That matrix is referred to K, correct ? It can be any letter so k2 is row 1 column 2 ?

It is just using a formula and a technique called plugging in. Nothing amazing about it.

I want to understand how it's 'plugging in' How do I figure this out, I know how you multiple a matrix and add so that helps.

bobbym · 2011-01-21 04:19:43

Hi;

K is that matrix but I do not care for or seen very much of that notation. A matrix in double indexed notation can be referred to as

That would mean 2 row, 2 column, so it would be 5. Sometimes in programming you might see:

K[1], that would mean the whole first row.

Plugging in is the act of substituting something for a variable. Usually a number. For instance 2x + 9. Plugging in a 5 for the x yields 19.

SuperLynx · 2011-01-21 04:46:00

K is that matrix but I do not care for or seen very much of that notation. A matrix in double indexed notation can be referred to as
That would mean 2 row, 2 column, so it would be 5.

This, I now understand

Sometimes in programming you might see:
K[1], that would mean the whole first row.

The whole first row being 1,2,3 ?!?!

Plugging in is the act of substituting something for a variable. Usually a number. For instance 2x + 9. Plugging in a 5 for the x yields 19.

I don't understand how you got 19 and how to figure out a determinant from a 3x3 matrix or especially a 4x4 matrix.

bobbym · 2011-01-21 05:02:33

Yes, that is the first row. Remember I told you that a matrix can be thought of as a collection of column vectors or row vectors. The first row is a row vector.

When you plug in to a variable you replace it. For 2 y + 5 when I plug in 5 for y I get 2 * 5 + 5 = 15.

how to figure out a determinant from a 3x3 matrix or especially a 4x4 matrix.

One thing at a time. Those are best done by computer. A 4x4 is never attempted by hand unless the person is a real boob. A 3x3 is tedious but possible. To demonstrate a determinant we usually use a 2 x 2.

SuperLynx · 2011-01-21 09:38:00

Yes, that is the first row. Remember I told you that a matrix can be thought of as a collection of column vectors or row vectors. The first row is a row vector.

I assume that is where in 3D you convert Matrix to Vector which takes the first row of the matrix ?

When you plug in to a variable you replace it. For 2 y + 5 when I plug in 5 for y I get 2 * 5 + 5 = 15.

Explain that again I still don't understand

One thing at a time. Those are best done by computer. A 4x4 is never attempted by hand unless the person is a real boob. A 3x3 is tedious but possible. To demonstrate a determinant we usually use a 2 x 2.

The determinant of a 2x2 or 3x3 matrix is the cross between as in (A)(D) & (B)(C) ?

bobbym · 2011-01-21 10:26:25

Hi SuperLynx;

You have let us say:

When we plug in 5 for y, we take the boxed y and replace it with 5.

So 3*3 =9 and 9 + 10 = 19. Remember that is what a variable like y reperesents. It represents some number.

We will cover the determinant in just a minute. Let us concentrate on the plugging in for right now.

SuperLynx · 2011-01-21 10:32:58

Whether it be y,z,k,p all those are just variables which can be replaced with numbers. When I see a matrix that is all letters that is just being used as a place holder for whichever numbers they want to replace with ?

bobbym · 2011-01-21 10:35:43

Correct. Whatever numbers they want to put into each element. Every box of a matrix is called an element. We refer to them by numbers. That is their name.

SuperLynx · 2011-01-21 11:04:23

Can you give me an example which letters are only used ? I can try to figure it out ?

Remember how I asked you how do they figure out what a matrix to a vector is ? We know that a vector is X,Y,Z which row or column is extracted and used as the vector ?

bobbym · 2011-01-21 11:23:37

Whenever there is a general formula you will see only letters. They will be variables in which you put numbers ( for the time being ) into. That is what Algebra is.

You can multiply a matrix and a vector to produce a vector. Or as I told you, you can consider a matrix to be a bunch of vectors. You can pull them apart as column or row vectors.

SuperLynx · 2011-01-21 15:13:55

Whenever there is a general formula you will see only letters. They will be variables in which you put numbers ( for the time being ) into. That is what Algebra is.

Slowly it's making sense

You can multiply a matrix and a vector to produce a vector. Or as I told you, you can consider a matrix to be a bunch of vectors. You can pull them apart as column or row vectors.

I just put what you said in practice with matricies and vectors and although the first stage turned out to be garbage I did do something in my 3D program so I made slight progress

I don't understand 4x4 matrices and determinants and I'd like if you could give me a 3x3 matrix question for me to break down and solve. Normalize, Normalizes values as in to 1,2,3 etc ?

bobbym · 2011-01-21 16:27:27

You know how to normalize a vector?

SuperLynx · 2011-01-21 16:47:03

No, do you ?
What about 4x4 matrices and determinants ?

I have question to post but I will as soon as I learn some plain & fast latex code

Math Is Fun Forum

#226 2011-01-19 15:36:23

Re: Math Terms - Visually Described ?

#227 2011-01-19 15:44:14

Re: Math Terms - Visually Described ?

#228 2011-01-20 00:54:21

Re: Math Terms - Visually Described ?

#229 2011-01-20 05:39:05

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#230 2011-01-20 12:08:14

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#231 2011-01-20 12:16:19

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#232 2011-01-20 12:43:21

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#233 2011-01-20 14:23:43

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#234 2011-01-20 16:09:02

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#235 2011-01-20 16:14:29

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#236 2011-01-21 03:05:32

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#237 2011-01-21 03:22:24

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#238 2011-01-21 04:06:46

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#239 2011-01-21 04:19:43

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#240 2011-01-21 04:46:00

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#241 2011-01-21 05:02:33

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#242 2011-01-21 09:38:00

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#243 2011-01-21 10:26:25

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#244 2011-01-21 10:32:58

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#245 2011-01-21 10:35:43

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#246 2011-01-21 11:04:23

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#247 2011-01-21 11:23:37

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#248 2011-01-21 15:13:55

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#249 2011-01-21 16:27:27

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#250 2011-01-21 16:47:03

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