In given fig.
consider triangle ABC and triange BAD.
i.e. in `Delta ABC andDelta BAC`
`angle ABC= angle BCA` (given)
AB= BA ( same segment)
`angle BAC=angle ABD= 90^o ` (given)
Thus by ASA property `Delta ABC cong Delta BAC`
since congruent part of cobgruent triangles are equal . Therefore