A number "x"0 is said to be a "fixed point" of a function "f"("x") if "f"("x"0) = "x"0; in other words, if "f" leaves "x"0 fixed. The fixed points of a function can be easily found graphically: they are simply the "x" coordinates of the points where the graph of "f"("x") intersects the graph of the line "y" = "x". For example, the fixed points of the function "T"3("x") are 0, 1/2, and 1; they are marked by black circles on the following diagram: