The focal length is found by equating the general expression for y
and our particular example:
So we have:
This gives `p = 0.5`.
So the focus will be at `(0, 0.5)` and the directrix is the line `y = -0.5`.
Our curve is as follows:
Note: Even though the sides look as though they become straight as x increases, in fact they do not. The sides of a parabola just get steeper and steeper (but are never vertical, either).
Easy to understand math videos: