Tracing a graph in sagemath

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You can construct an interactive graph with a slider to trace the plotted function. As a proof of concept, you can check the interact given in this SageMath Cell. For the sake of completeness, I copy here the corresponding code:

f(x) = sin(2*x)-3*cos(x)
xmin = -2*pi
xmax = 4*pi
@interact
def _(xx=slider(xmin,xmax,default=xmin,label="x"), 
      trace=checkbox(default=False,label="Trace")):
    p = plot(f(x), (x,xmin,xmax), color="green")
    if trace:
        p += text(r"$({0:f},{1:f})$".format(float(xx),float(f(xx))),(xx,f(xx)), 
                  color="black", vertical_alignment="top")
        p += point((xx,f(xx)), color="red", size=30)
    show(p)