∴ – therefore

|**x**| = Euclidian Length i.e. the pythagorean hypoteneuse √((x’-x)^2+(y’-y)^2)

≈ – approximately equal to

⇒ implies

∀ – for all, any & each… e.g. ∀ *x*: *P*(*x*) for all x P is true

∃ – there exists a… e.g. ∃ *x*: *P*(*x*) There is an x such that P is true

ℝ – Real numbers , x ∈ ℝ – x is a real number

∑ – summation i.e. means .

∏ – product means .

Δ – delta , change in… Δx – change in x

∂ – partial derivative i.e. ∂E/∂y – Change in E as y changes. Also the slope or gradient of the line (E,y). Useful for Stchastic Gradient Descent in Neural Net Backpropagation.

T – Matrix Transpose — *A*^{T} means *A*, but with its rows swapped for columns. Also A’

MathML – does it work – http://en.wikipedia.org/wiki/MathML ? not in Firefox 18.0.2 OOTB but it’s supposed to. grrrrrr

math mode=”display” xmlns=”http://www.w3.org/1998/Math/MathML”

Firemath ? www.firemath.info/examples/ — doesn’t work in FF 18