# Talk:Matrix

## Checklist

### Is this just a helper page?

• Yep, it's a helper page on matrix algebra with a discussion of matrix entries, properties and notation.

### Message to the future

• Maybe add more to the "Matrices as Functions" section? It might make the page too long, though.

### References and footnotes

• The few images in the page are referenced
• There are no direct quotes.

### Good Writing

#### Quality of Prose and page structuring

• The beginning paragraphs were significantly changed to address the confusion over expressing matrices.
• Sections are broken up clearly to indicate which specific matrix operation is being addressed
• Within More Mathematical Section, heaviest math-proofs of the matrix properties are placed as deep into their respective subsections as possible-even under a Hide function.

#### Integration of Images and Text

• The readers are referred specifically to the animation.
• The text points out why the animation is there-to explain how to do matrix multiplication
• Readers are referred specifically to image that follows after matrix transposition. The text even explains what is going on with the transposition image. Only problem is that the transposition image itself has a grammatical typo that canâ€™t be fixed.

#### Connections to other Mathematical Topics

• Connections made at the beginning of the page, where this Helper Page links back to other topics shown under the Yellow Box
• Other connections made at the bottom of the page, where matrices represent functions.

#### Examples, Calculations, Applications, Proofs

• Numerical examples are provided for each new matrix concept.
• Proofs are included for properties of each matrix operation.

#### Mathematical Accuracy and precision of language

• All proofs are free of mathematical errors.
• Statements for proofs still need to be made precise, especially when explaining steps needed to arrive at certain manipulations of matrices in the middle of proofs.
• Mouse overs included in statements of matrix properties.

#### Layout

• Paragraphs are kept short with matrices throughout.
• The animation and the matrices are fully contained in the correct sections.
• The page looks good at most sizes. At extremely thin sizes, some equations stick off of the side a bit, but I don't think that there is any feasible way to avoid that.

# Old Feedback

Smaurer1 18:22, 31 May 2013 (EDT) The link at the bottom to another discussion of matrices seems to be a dead link now. If others agree, take it out.

Cwang3 15:39, 5 June 2013 (EDT)

About the comment above: I agree that the link at the bottom does not work and should be taken out.

I think now the layout of the page is pretty clear, and here's some feedback for Jason's parts:

1. Proof that Matrix Multiplication is Associative: I think the proof might look nicer if "WTS" is not in math environment. You can try different ways and see which one works best. Also, the equations after lines "By Definition" and "By Associativity" can be moved to a newline.

2. Proof that Matrix Multiplication over Addition is Distributive: (I just realized that this is Lucy's part, but I'll leave the comments here anyway)

WTS and proof part, it's supposed to be A(B+C), not A+B+C.

It's clearer if you leave more space between the equation and the short explanations ("By definition", "By addition", etc.).

Be consistent with whether you capitalize the letters in your equation. Sometimes you use Aij, sometimes ai,j

3. Matrix Transposition: Maybe make a simple graph to illustrate how transpose is done? For example, use arrows to show which entry goes to where, or an animation showing the move of the columns.

Cwang3 10:39, 12 June 2013 (EDT)

1. Section "Size", are you sure the size is column by row? I think it should be row by column. (m × n matrix has m rows and n columns)

2. Proof of Matrix Multiplication is Associative: "communicative" should be "commutative"

The major change I just made to this page was in accordance to the document I received from Steve Cunningham, and the content was written by him. I did the formatting of the page. If someone wants/needs to restore this page to the way it was before I made this change, it was all done in my only edit to this page today (so it can easily be undone).

Nordhr 17:43 12 July 2011

## Last Edits for now

Jason and I are going to take another look at the matrix page. But as of today this will be the last edit we will make on the page for a long time. Not until the last week of the Project will we attempt to go back and edit it again. Dated: Thursday June 20 2013