Answer:
Triangles ABC and ADC are congruent because they all have the same angles. AC bisects angle A which means that both triangles have the same angle measurement. C is a 180 degree angle and is bisected, meaning that both angles created are 90 degree angles and thus the same degree measurement.
Another reason why they are congruent is because the sides are equal. AB and AD are the same length because the picture shows a singular line on both sides meaning they are the same. The height of both triangles are the same because they share a height. BC and CD are the same length because AC is bisecting BD, meaning both sides are equal in length. Thus, both triangles have the same side measurements.