Answer: It seems you're looking to plot the function f(x) = 1 + cos(x/2) for different values of n, within the range -π ≤ x ≤ π. However, your question isn't quite clear because you mention n = 3, 4, 6, but don't explain how n is related to the function. In your function f(x) = 1 + cos(x/2), there is no variable n.
If n is a parameter that affects the function in some way, you need to specify how it does so before the function can be evaluated or plotted for different values of n.
If n is intended to represent the number of divisions within the interval -π to π, then this would affect the granularity of the plot but not the function itself. For example, if n=3, you'd evaluate the function at -π, 0, and π. If n=4, you'd evaluate it at -π, -π/2, π/2, and π. And so on.
If you could provide some additional information or clarification about how n is supposed to interact with your function, I would be able to provide a more accurate response.