Q:

Find a matrix $B$ so that $A = BB^{T}$

$A$ is
$$A=
    \begin{pmatrix}
    2 & 0 & 1 \\
    0 & 2 & 0 \\
    1 & 0 & 2 \\
    \end{pmatrix}
$$
Find a matrix $B$ so that $A=BB^{T}$. Hint: $A=PDP^{T}$.

A:

Hint: since $D$ is diagonal, you can take its square root $\sqrt{D}$. Then define
$$B\equiv P\sqrt{D}$$

