Answer
$2\sqrt2-2\sqrt2i$
Work Step by Step
By computing using the given values:
$4\cdot (\cos {(\frac{7\pi}{4})}+i\cdot \sin{(\frac{7\pi}{4}))}
\\=4\left(\frac{\sqrt2}{2}-i\frac{\sqrt2}{2}\right)
\\=2\sqrt2-2\sqrt2i$
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