how can i prove the reflexive property of triangle congruence?

Question

i need to prove it in two column. 

Answer 1

The reflexive property of triangle congruence definition:

The mirror image of any triangle is always congruent to it.

Solution: Select two columns and a draw a triangle on column #1.

Then draw a second triangle (as a mirror image of the first one ) in column #2.

The second triangle has all three sides of the same length with the first triangle, because they are mirror image. Therefore, both triangles are congruent.