Math Is Fun Forum

jetsetwilly

Member

Registered: 2005-11-03

Posts: 1

y = mx + c. Why m?

Why is the letter m used to denote the gradient of a line? Why not g?
Got asked this in class and I didnt know the answer.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: y = mx + c. Why m?

I think it's just convention. I don't know how that convention started though.

---

Why did the vector cross the road?
It wanted to be normal.

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: y = mx + c. Why m?

Found this:

The earliest known use of "m" for slope is from an 1844 British text by Matthew O'Brien entitled "A Treatise on Plane Co-Ordinate Geometry". Later in 1848 George Salmon (1819-1904) referred to O'Brien's 1844 article within his "A Treatise on Conic Sections" and used the slope-intercept formula "y = mx + b", where "b" is the ordinate (vertical component) of the point where the line intersects the y-axis. It is also known that the four authors Isaac Todhunter in 1855 (Treatise on Plane Co-Ordinate Geometry), George A. Osborne in 1891 (Differential and Integral Calculus), and Arthur M. Harding and George W. Mullins in 1924 (Analytic Geometry) each used "m" to refer to slope in their mathematical writings.

(Source: http://www.bookrags.com/sciences/mathematics/slope-wom.html)

---

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

Curunen

Member

Registered: 2005-09-19

Posts: 12

Re: y = mx + c. Why m?

wow. It might be good if a new alphabet was made, so that you didn't end up with multiple meanings for a symbol.

---

Techniques are many, Principles are few.
Techniques may vary, Principles never do.