SSS (Side-Side-Side) Postulate
If the three sides of a triangle are congruent to the three sides of another triangle, then the two triangles are congruent.
In the figure, 
.
Therefore, by the SSS postulate, 
.
If the three sides of a triangle are congruent to the three sides of another triangle, then the two triangles are congruent.
In the figure, .
Therefore, by the SSS postulate, .