Is the following correct ?? And is there a proof for this ?
$\| c - d\|^2 = \| c\|^2 + \|d \|^2 - 2cd$
Another question: Why is the following true ?? I do not understand how it goes from LHS to RHS. (Notice the thing below actually comes from the proof of Jame-Stein Estimator)
$\left\| \frac{X}{\|X\|^2} \right\|^2 = \frac{1}{\|X\|^2}$