Question

how to construct an altitude of a right triangle from the vertex containing right angle

Answer 1

To construct the perpendicular in right triangle from the vertex with right angle follow thesteps:

Let say Triangle IS ABC with Angle B as right angle.
a) Taking B as a center open the compass draw an arc on AC which cuts it at two points E and F.
b) Taking E and F as center draw the bisector of an arc at G (say).
c) Join BG which cuts AC at H.

BH is required perpendicular to AC.