Let Γ1 and Γ2 be arbitrary circles that intersect at points P and Q.
Prove or disprove that there exist points M and N such that
(1) M ∈ Γ1\{P,Q},
(2) N ∈ Γ2\{P,Q},
(3) M, N, and P are collinear, and
(4) ∠MQP = ∠NQP.
If they exist, prove or disprove that they can be constructed with
straightedge and compass.
Here is a link to Wolfram MathWorld:
Definition of Set Difference