Mathematics desk
< August 29	<< Jul \| August \| Sep >>	August 31 >

Welcome to the Wikipedia Mathematics Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

August 30[edit]

Right triangle[edit]

How do you determine the length of the long side of a right triangle? —Preceding unsigned comment added by Lafaber mabel (talk • contribs) 16:59, August 30, 2007 (UTC)

You may find the Pythagorean theorem to be of use. — Lomn 17:02, 30 August 2007 (UTC)[reply]

Unless you live in a curved space, of course. —Tamfang 20:15, 2 September 2007 (UTC)[reply]

Gradient[edit]

Why is it that in the formula for the gradient $m={\dfrac {y_{2}-y_{1}}{x_{2}-x_{1}}}$ , where you have two points labelled $(x_{1},y_{1})$ for the first co-ordinate and $(x_{2},y_{2})$ for the second, the letter "m" is used for gradient? Thanks, 81.151.242.78 17:31, 30 August 2007 (UTC)[reply]

You could use any letter. What's wrong with "m"? —Bromskloss 17:36, 30 August 2007 (UTC)[reply]

You could, yes, but 'm' is traditional for the gradient of a line. No idea why, though. This was asked at Talk:Slope last year, but no answers there yet. Algebraist 18:13, 30 August 2007 (UTC)[reply]

It's a good question (and a popular one) see http://mathforum.org/library/drmath/view/52477.html amongst possibles of "modulus of slope" or "monter" - (french) to climb this to me seems as near as one will get (from a maths teacher in quebec) see article:

...His answer was approximately: "In our system, the first letters of the alphabet, a, b , c... represent the constants, the last letters, x, y, z represent the unknown variables and the middle letters, m, n, p... represents the parameters. When we started the explanations of slope, it was in studying the first degree equation: y = mx + b. x and y were the variables, b was fixed and considered as a constant, and what was appended to the coefficient of x as its value varied. So it was a parameter and that is why we used m."

I tend to do the same and so tend to agree...213.249.232.26 18:39, 30 August 2007 (UTC)[reply]

Hmm, usually a,b,c,d are constant real parameters; f,g,h are functions, i,j,k,l,m,n are integer parameters or indeces; x,y,z and if needed w,s,t are variable arguments. (Igny 04:27, 31 August 2007 (UTC))[reply]

Mmmh, when? (examples?)213.249.232.202 07:24, 31 August 2007 (UTC)[reply]

example:

y_{ij}=\sum _{k,m,n}f_{k}(a_{i}x_{mn}+b_{j})

(Igny 13:44, 31 August 2007 (UTC))[reply]

Oh yes. Good example - the question was about gradients anyway...87.102.88.202 14:50, 31 August 2007 (UTC)[reply]

While on the topic of traditional notation… While at university (I recently graduated, yay!) I was a teaching assistant at the maths department. As I was teaching my class, I used "q" for something that was usually represented by some other letter. Later, when I was processing assignments together with the other teaching assistants, some students could be spotted as mine because they used "q" as well. I had kind of left a watermark in my teaching and could see how it had spread. :-) —Bromskloss 19:14, 30 August 2007 (UTC)[reply]

I think your example is a pretty good illustration of how 'm' for slope has come about - your next step would be to write a maths text book (using q) then come back in 20 years time and then respond to questions such as "why is q always used for a variable"213.249.232.202 06:53, 31 August 2007 (UTC)[reply]

Note, however that the French word for slope is pente. deeptrivia (talk) 19:30, 30 August 2007 (UTC)[reply]