Question

D is the midpoint on BC such that angle ABD equal to angle CAD

Answer 1

To prove : angle ABD = 90
Proof:
angle ABD = angle CAD
( coz they form a linear pair)
but angle ABD=CAD
So, ABD + CAD =180
2 × ABD= 180
angle ABD = 90
So ABD=CAD=90
Hence, proved