Do you want to convert the value (0..1023) to an angle?
assuming you do:
consider 0,0 as the midpoint of the arc, and R its radius,
float alpha = 180 - analogRead(A0) / 5.68333;
int x = R * cos(alpha):
int y = R * sin(alpha);
line 0,0, x, y;
you need to keep the XY value to clear the line before drawing the next;