Much more of the character of the multiplication of complex numbers is revealed through this representation. The polar coordinates of the complex unit i are given by(1,90°).(Normally,angles are not measured in degrees in such circumstances but in the natural mathematical unit of the radian:there are 2π radians in a circle, so that a turn of one radian corresponds to moving one unit along the circumference of the unit circle, centred at the origin. One radian is about 57.3°.)Ifwe now take any complex number z=(r,θ)and multiply by i=(1,90°), we find that zi=(r,θ+90°). That is to say, multiplication by i corresponds to rotation through a right angle about the centre of the complex plane. In other words, the right angle, that most fundamental geometric idea, can be represented as a number.