# Chapter 8 - Test - Page 412: 5b

$\sqrt{5}cis63.43^\circ$ or $\sqrt{5}(cos 63.43^\circ + isin63.43^\circ)$

#### Work Step by Step

$1 + 2i$ is at $arctan(\frac{2}{1}) = 63.43^\circ$ with absolute value $\sqrt{1^2 + 2^2} =\sqrt{5}$, the equivalent trigonometric form is $\sqrt{5}cis63.43^\circ$ or $\sqrt{5}(cos 63.43^\circ + isin63.43^\circ)$.

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