What is the term for an anti-clockwise rotating vector used to help graph sinusoidal functions?

The term you are looking for is "phasor." A phasor is a representation of a sinusoidal function as a rotating vector in the complex plane. It simplifies the analysis of sinusoidal waveforms, particularly in electrical engineering and physics, by allowing us to use vector addition to combine sinusoidal functions.

When visualizing a sinusoidal function, a phasor rotates in a counterclockwise direction, representing the changing amplitude and phase of the waveform over time. This aids in understanding concepts like phase differences and the addition of sinusoidal signals, making calculations more efficient than dealing with real-time oscillations directly.

Other terms such as vector and scalar do not accurately describe the specific concept of representing sinusoidal functions by rotation in the complex plane. Amplitude refers to the maximum value of a sinusoidal function and is not related to the direction or rotation aspect of the phasor. Thus, "phasor" is the most accurate term for this context.