$$<br /> \begin{align*} <br /> i &amp;=\sqrt{-1} \\<br /> i^1 &amp;=i^\frac{4}{4} \\<br /> i &amp;=\sqrt{-1}^{4\frac{1}{4}} \\<br /> i &amp;=1^{\frac{1}{4}} \\<br /> i &amp;=1<br /> \end{align*}<br />$$