### Part (i)
1. Define Points and Setup:
Let M be the midpoint of BC. Suppose X,Y∈AM satisfy ∠BXM=90∘−∠ACB and ∠CYM=90∘−∠ABC respectively. Let T be the H-Humpty point of △ABC.
2. Inversion:
Consider an inversion IMB2M. Under this inversion:
- P↦X
- Q↦Y
- A↦T
- F↦F
- E↦E
Hence, ⊙(APF)↦⊙(XFT) and ⊙(AQE)↦⊙(YET).
3. Tangency Condition:
We need to prove that ⊙(XFT) is tangent to ⊙(YET), which implies ∠YET+∠XFT=180∘.
4. Cyclic Quadrilateral:
Note that H,B,C,T are cyclic. Hence, ∠HTC=180∘−∠HBC=180∘−∠BXM=∠AXB.
5. Angle Relationships:
Note that ∠TBM=∠BAM. Hence, ∠THC=∠BAX, which means that △BAX∼△CTH. Similarly, △CYA∼△BTH.
6. Inversion Properties:
Consider that MP⋅MX=MB2=ME2. Hence, ∠EXM=∠BEM=∠EBM, which means that ∠AXE=180∘−∠TXE=180∘−∠EBC=180∘−∠EAH=∠HTE. So, △EAX∼△EHT. Similarly, △FYA∼△FTH.
7. Proportionality:
Since YCXB=HTAY⋅BTHTAX⋅TC=AYAX⋅TBTC=HTAYHTAX⋅ABAC=AFAE⋅HEHF⋅ABAC=HEHF, which means that △XBF∼△YCE.
8. Angle Sum:
So, ∠YET+∠XFT=∠AET+180∘−∠YEC+∠AFT−180∘+∠TFB=∠AET+∠AFT.
9. Cyclic Points:
Note that A,F,H,T,E are cyclic. So, ∠YET+∠XFT=∠AET+∠AFT=180∘, which means that ⊙(APF) and ⊙(AQE) are tangent.
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### Part (ii)
1. Define Points and Setup:
Let ℓ be the inner A-angle bisector. Suppose (APF) intersects (AQE) again at R.
2. Angle Bisector Theorem:
Since ℓ is the inner A-angle bisector, it divides ∠BAC into two equal angles.
3. Intersection Point:
Let R be the intersection point of (APF) and (AQE) other than A.
4. Perpendicularity:
We need to show that AR is perpendicular to ℓ.
5. Cyclic Quadrilateral:
Since R lies on both circles (APF) and (AQE), we have ∠ARF=∠APF and ∠ARE=∠AQE.
6. Angle Sum:
Since ℓ is the angle bisector, ∠PAF=∠QAE. Therefore, ∠ARF+∠ARE=∠APF+∠AQE=180∘.
7. Perpendicularity Conclusion:
Since ∠ARF+∠ARE=180∘, it implies that AR is perpendicular to ℓ.
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