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

% DET: points B and T_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 C and the point B, construct a point M_a (rule W01);

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

% DET: points O and M_a are not the same

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

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

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

% DET: points N_a and T_a are not the same

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

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

% DET: points N_a and A must be different