# Complex rotation

Multiplying a real or complex number by the imaginary unit $j$ corresponds to a rotation by $+90^{\circ}$. This is the key feature of $j$ that makes it such a useful number.

Created by Willy McAllister.

Multiplying a real or complex number by the imaginary unit $j$ corresponds to a rotation by $+90^{\circ}$. This is the key feature of $j$ that makes it such a useful number.

Created by Willy McAllister.