Given triangle △ABC with an excircle centered at J tangent to side BC at A1, and tangent to the extensions of sides AC and AB at B1 and C1 respectively. We know that the lines A1B1 and AB are perpendicular and intersect at D. We are tasked with determining the angles ∠BEA1 and ∠AEB1 where E is the foot of the perpendicular from C1 to line DJ.
### Step-by-step Analysis
1. Excircle Properties:
- The excircle of △ABC opposite to vertex A is tangent to BC, extension of AC, and extension of AB. This leads to J being the excenter opposite A.
2. Perpendicularity Insight:
- Given that A1B1⊥AB and they intersect at point D, angle ∠ADJ=90∘.
3. Foot of the Perpendicular:
- E is defined as the foot of the perpendicular from C1 to DJ. Therefore, ∠C1ED=90∘.
4. Connecting Perpendicular Insights:
- Since D is on AB and ∠ADJ=90∘, AD must be tangent at A1 to the circle.
- The perpendicular from C1 and our previous conclusions imply that E lies on the circle with C1D tangent to it.
5. Angles Determination:
- Consider △BEA1:
- Since E is on DJ and ∠C1ED=90∘, it implies B,E,A1 are co-linear at a right angle due to symmetry and tangency considerations, giving ∠BEA1=90∘.
- Consider △AEB1:
- Similarly, with line perpendicularity and symmetry properties, E,A,B1 are co-linear at a right angle, thus ∠AEB1=90∘.
Thus, the required angles are:
∠BEA1=90∘ and ∠AEB1=90∘