This is plug-n-chug.
Use the given point and calculated slope to create a linear approximation of the next point.
Point: (0,0) Slope: 1 - (0)(0) = 1 Line: y = x Next Point: y = 0.2
Point: (0.2,0.2) Slope: 0.96 Line: y-0.2 = 0.96*(x-0.2) New Point: y = 0.392
And so on. In this case, you should see that it wanders off a bit. I get an absolute error of around 0.06 by the time you're done.
Note: You don't REALLY have to write the equation of the line in each step. That was just for your benefit. Use a little algebra to create more convenient formulations, maybe
.