This is meant to demonstrate the epsilon-delta definition of a limit.

This shows the graph of the square root function, with *x* = 4 being sent to
*y* = 2.

What to do:

- Change the value of ε (epsilon) by clicking and dragging up or down the green spot
on the top edge of the epsilon region near the
*y*-axis. - Change the value of δ (delta) by clicking and dragging left or right the green spot on the right edge of the delta region near the
*x*-axis. - Change the value of
*x*by clicking and dragging the green spot just above the number (which is initially set at 4.567).

So with this diagram, you can see that if *x* is within δ units of 4, then *y* is
within ε units of 2.