Final answer:
A phase shift in sinusoidal functions represents a horizontal shift along the x-axis and is determined by a value inside the function's argument. In y = 2cos(3(x + 2π/5)), the phase shift is 2π/5, indicating the cosine graph is shifted to the left by that amount.
Step-by-step explanation:
The term phase shift refers to the horizontal shift of a sinusoidal function along the x-axis on a graph. In the equation y = 2cos(3(x + 2π/5)), the phase shift is determined by the expression inside the parentheses next to the x, which in this case is 2π/5. This means that the graph of the cosine function is shifted to the left by 2π/5 units. In general, for the function y = A cos(ωt + φ) or y = A sin(ωx - φ + p), the phase shift is given by the value of φ (phi), which determines how much the function is shifted horizontally on the graph.