Namgyun Lee Deleted File  about 8 years ago

Commit id: 47cdc3ea80fffe3f165219e7ffc5c02f14f1a0c3

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\paragraph{Example 2.}  Given $x \in \complex^n$, What is $D\|x\|^2$? \\  %We have  %\begin{align*}  % |x| &= \sqrt{x^*x} = \sqrt{(a-jb)(a+jb)} = \sqrt{a^2 + b^2}. \\  %\end{align*}  %Then,  %\begin{eqnarray}  % D|x| &= \frac{d|x|}{da} + j\frac{d|x|}{db} \\  % &= \frac{2a}{2\sqrt{a^2 + b^2}} + j\frac{2b}{2\sqrt{a^2 + b^2}} \\  % &= \frac{a}{\sqrt{a^2 + b^2}} + j\frac{b}{\sqrt{a^2 + b^2}} \\  % &= \frac{x}{|x|}.  %\end{eqnarray}