HELP WITH A GRAPH

As Valery says, if you want to plot Y against X then either Y must be a function of X, in which case X must appear on the rhs of the function definition, or both X and Y must be functions of another variable that appears on the rhs of both function definitions (a parametric plot). I can plot

Y(X):=sin(X)

or

Y(A):=sin(A)

X(A):=cos(A)

but I cannot plot

Y(X):=sin(A)

I set yours up as a simple x-y plot, but it could also be done as a parametric plot.