Using the point B and the point H_a, construct a line a (rule W02);

% DET: points B and H_a are not the same

Using the point B and the point O, construct a circle k(O,C) (rule W06);

% NDG: points B and O are not the same

Using the circle k(O,C), the line a, the point O and the point B, construct a point C (rule W05);

% NDG: line a and circle k(O,C) intersect

% DET: points B and C must be different

Using the point H_a and the line a, construct a line h_a (rule W10b);

Using the circle k(O,C) and the line h_a, construct a point A_k and a point A (rule W04);

% NDG: line h_a and circle k(O,C) intersect