A statement which appears to be true but has not been proven to be so, is a postulate.
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.
To determine if triangle MNO is congruent to triangle PQR, we need to compare their corresponding sides and angles. If they are equal in length and measure, then MNO is congruent to PQR. The specific congruence postulate that could apply is the Side-Angle-Side (SAS) postulate, which states that if two sides and the included angle of one triangle are equal to two sides and the included angle of another triangle, the triangles are congruent.
Might not be congruent
OK, so know your alphabet. Very good. How fast can you say it backwards?
SAS
not congruent
Congruent - SAS
congruent - asa
Congruent - SSS
similar - AA
not congruent
yes
APEX Congruent-SAS
A statement which appears to be true but has not been proven to be so, is a postulate.