There are several ways two triangles can be congruent.
<em> congruent by SAS</em>
<em> congruent by corresponding theorem</em>
In
and
(see attachment), we have the following observations
--- Because O is the midpoint of line segment AD
--- Because O is the midpoint of line segment BC
---- Because vertical angles are congruent
---- Because vertical angles are congruent
Using the SAS (<em>side-angle-side</em>) postulate, we have:

Using corresponding theorem,
---- i.e. both triangles are congruent
The above congruence equation is true because:
- <em>2 sides of both triangles are congruent</em>
- <em>1 angle each of both triangles is equal</em>
- <em>Corresponding angles are equal</em>
See attachment
Read more about congruence triangles at:
brainly.com/question/20517835