Analysis: establish parabolic function relationship, establish coordinate system with straight line of AB as X axis and vertical line of AB as Y axis, then get the coordinates of points A, B, C and D, and substitute them into the function to solve.

Solution: If the coordinate system is established, you can get the coordinates of point A (-4,0), point B (4,0), point C (-3,4) and point D (3,4).

Let the parabolic function be y=ax? +bx+c, substitute the coordinates of points into the function to get:

{? 16a-4b+c=0，

16a+4b+c=0，

9a-3b+c=4，

Solution: a=△, b=△, c=△.

The function is y=△,

That is, the coordinate of point E is (△, 0),

∴: The height of the doorway is △ meters.

Just figure it out yourself.