1. **Identify the common point M:**
Let M be the common point of the circumcircles of △ABC and △ADE. Since M lies on both circumcircles, it must be the center of the spiral similarity that maps BD to CE. Given that BD=CE, M must be the midpoint of the arc BAC on the circumcircle of △ABC that does not contain A.
2. **Angle chasing to show ∠O1OA=∠O2OM:**
Since M is the midpoint of the arc BAC, we have:
∠BAM=∠CAM
This implies that:
∠BAM=∠CAM=21∠BAC
Since O1 and O2 are the circumcenters of △ABE and △ACD respectively, we have:
∠O1AO=∠O2AO=90∘−21∠BAC
Therefore:
∠O1OA=∠O2OM
3. **Prove that OO1=OO2:**
To show that OO1=OO2, we observe the following:
- △BOO1∼△BEC
- △COO2∼△BED
Using the Law of Sines in △ABE and △ACD, we get:
OO2OO1=∣BE∣⋅∣CO2∣∣DC∣⋅∣BO1∣
Since BD=CE, it follows that:
∣BE∣∣DC∣=1
Therefore:
OO2OO1=1⟹OO1=OO2
4. **Conclude that AO1O2M is cyclic:**
Since OO1=OO2 and ∠O1OA=∠O2OM, we have:
△AOO1∼△MOO2
and
△MOO1∼△AOO2
This implies that AO1O2M is an isosceles trapezoid, which is cyclic.
Therefore, the circumcircles of △ABC, △ADE, and △AO1O2 have a common point different from A.
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