COnsider the figure,
Two triangles are said to be congruent if all their three sides and three angles are equal.
SInce angle K and N are both right angles, we have,
The side ML is the shared side, and hence equal for both the triangles.
SInce LM bisects angle KLN, we have,
Thus, from AAS theorem ( stands for Angle-angle-side), when two angles and a non-included side of a triangle are equal to the corresponding angles and sides of another triangle, then the triangles are said to be congruent.
Hence the triangles are congruent.