A statement which appears to be true but has not been proven to be so, is a postulate.
If you are referring to the congruence of triangles formed by segments labeled as "a," "b," "c," "d," "e," and "f," the applicable postulate would depend on the specific relationships between these segments. For example, if two triangles share two sides and the included angle, you could apply the Side-Angle-Side (SAS) Congruence Postulate. Alternatively, if they have three sides of equal length, you would use the Side-Side-Side (SSS) Congruence Postulate. More details about the relationships would help clarify which postulate applies.
None; because there is no justification for assuming that the two triangles (or trangles, as you prefer to call them) are similar.
similar - SAS
Euclid's second postulate allows that line segment to be extended farther in that same direction, so that it can reach any required distance. This could result in an infinitely long line.
Might not be congruent
OK, so know your alphabet. Very good. How fast can you say it backwards?
SAS
not congruent
Congruent - SAS
Congruent - SSS
congruent - asa
not congruent
similar - AA
yes
APEX Congruent-SAS
A statement which appears to be true but has not been proven to be so, is a postulate.