I've never done matrix differentiation before, and I want to differentiate this:

$\displaystyle (Y-X\theta)^{T}(Y-X\theta)$ with respect to $\displaystyle \theta$. I'm told that, using the product rule, we get:

$\displaystyle 2X^{T}(Y-X\theta)$.

(In the above, X, Y and $\displaystyle \theta$ are all column matrices). Can someone very quickly run through this for me please? Thanks.