Using the point A and the point T_a, construct a line s_a (rule W02);

% DET: points A and T_a are not the same

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

% NDG: points A and O are not the same

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

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

% DET: points A and N_a must be different

Using the point N_a and the point O, construct a line m_a (rule W02);

% DET: points N_a and O are not the same

Using the point T_a and the line m_a, construct a line a (rule W10a);

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

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