From Gogeometry Using Additional points Inscribed angles in a circle congruent triangles Thales theorem Concyclic points ∠DBC = ∠DBA+∠ABC = π/2+∠ABC∠ABG = ∠ABC+∠BCG = ∠ABC+ π/2=> ∠DBC = ∠ABG=> Δ DBC is congruent to Δ ABG (SAS)=> ∠BDC = ∠BAG and DC=AG Define K the intersection of AG and BC=> […]