Calculate reflection matrix given normal vector

Question

Let $A$ be origin plane in ${\Bbb R}^3$ given normal vector $n = (x,y,z)$. $T = {\Bbb R}^3 \to {\Bbb R}^3$.

How do I go about calculating the reflection matrix $T$?

Given is the following formula

$$ T(v) = v-2\frac{v \cdot n}{n \cdot n} n $$