Suppose you have a $2\times 1$ column vector $x=[7,2]^{T}$. How would you find $||x||^{2}$? Would it be $7^{2} + 2^{2}$? Is this equivalent to the distance from the origin?
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$\begingroup$Yes, for a $t \times 1 $ vector $x$, we have $\|x\| = \sqrt{\sum_{i=1}^t |x_i|^2}$, where $x_i$ is the $i$th component of $x$, and $\|\cdot\|$ is the usual Euclidean distance. $\|x\|$ (not $\|x\|^2$) is the distance of $x$ to the origin. You may verify this via the Pythagorean theorem. Draw your 2D vector $[x_1\, x_2]^T$ and calculate its distance to the origin.
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