Call A_b, A_c the reflection of A on lines BI and CI, respectively. Define B_c, B_a and C_a, C_b analogously.
Then line segments B_cC_b, C_aA_c and A_bB_c are parallel. They are also proportional to the sides of ABC and we have the ratios B_cC_b/BC = C_aA_c/CA = A_bB_a/AB = OI/R.
The common infinite point of lines B_cC_b, C_aA_c and A_bB_c is the isogonal conjugate of the point X_{100}.
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