On a similar note, a complex sinusoid rotating clockwise with a frequency $F$ is a single impulse at $-F.$ In the above figure, observe the direction of rotation of the sinusoids and the corresponding positive and negative frequency impulses. In general, when a signal is drawn in frequency domain, the graph actually shows the $I$ and $Q$ amplitudes of those complex sinusoids whose frequencies are present in that signal. To gain some insight into the relation between phase angle in I/Q plane of one domain and the phase shift of a sinusoid in I/Q plane of the other domain, let us recall the frequency domain idea above: A unit impulse in one domain (e.g., frequency) corresponds to a complex sinusoid in the other domain (e.g., time).