Refer to the following figure:
Which line segment depicts the “height” of point A from the base BE?
Given that ∠ADE = 90∘ and ∠ABC = ∠AEB
Height is the shortest distance of a point from a reference level. In our case, our reference level is the horizontal level BE.
The vertical distance is AD (∠ADE = 90∘) is the smallest distance of A from BE.
To prove this, let us join any other point on BE(say C) and A. Then we have a right triangle CAD of which AC would become the hypotenuse and hence is the longest side.
Therefore AD is the shortest and hence is the height.