Final answer:
The question refers to the concept of geometric congruence, where two triangles are congruent if all corresponding sides and angles are equal. Specific angles of coincidence would depend on the side lengths and angles of each triangle, which are not provided in the question.
Step-by-step explanation:
The question appears to involve the concept of triangle congruence in geometry. Without additional context, it is unclear how Δ a' b' c' might coincide with other triangles such as Δ abc, Δ def, Δ ghi, or Δ jkl. Geometric congruence relies on properties such as side lengths and angles being identical between triangles. The specific angles at which these triangles coincide would depend on their respective angles and side lengths. If given that these triangles are in fact congruent, then they would coincide when they are rotated or positioned such that their corresponding sides and angles match.
To demonstrate congruence between triangles or understand when one triangle will coincide with another, one must consider criteria like Side-Side-Side (SSS), Side-Angle-Side (SAS), Angle-Side-Angle (ASA), and Angle-Angle-Side (AAS).
Without further information, it's not possible to give a specific answer to the angles at which Δ a' b' c' will coincide with the other listed triangles.