I_{2} is ahead of I_{1} by π/2 (or 90°), since the rotation of the phasors is counterclockwise

Let us assume that a certain quantity I(t) changes over time as I(t) = I_{0}cos(ωt). A phasor is a vector whose length represents the amplitude I_{0} (see the diagram (Figure 1) ). This vector is assumed to rotate counterclockwise with angular frequency ω, that way, the horizontal component of the vector represents the actual value i(t) at any given moment. In this problem, you will answer some basic questions about phasors and prepare to use them in the analysis of various AC circuits.

At the moment t depicted in the diagram, which of the following statements is true?

A) I_{2} leads I_{1} by π

B) I_{1} leads I_{2} by π

C) I_{2} leads I_{1} by π/2

D) I_{1} leads I_{2} by π/2