Polar Coordinates and Complex Numbers · Easy problem

$2\left(\cos 90^\circ+i\sin 91^\circ\right)$

$4\left(\cos 90^\circ+i\sin 90^\circ\right)$

$-2\left(\cos 90^\circ+i\sin 90^\circ\right)$

$2\left(\cos 90^\circ+i\sin 90^\circ\right)$