Given:
Three right angled triangle are given. Triangle ABC right angled at B , triangle BDC right angled at D and triangle ABD right angled at D.
The objective is to find which side of triangle ABC is correspond to the side AB in triangle ABD.
Consider the right angled triangle ABC right angled at B. So let's take AB as the base.
Also consider right angled triangle ABD right angled at D. So the side AD will be the base of the triangle.
Hence, side AD of triangle ABD is correspond to side AB of triangle ABC.