Perpotongan dua garis

\coordinate (R) at ($(D)!1cm!-90:(E)$);
\path[name path=g1] (P)--($(B)!-3.5cm!(P)$);
\bagisudut[draw,red!50,thin,name path=gbs]{R}{D}{E}{1.5}{2}
\path[name intersections={of = gbs and g1, by={A}}];
\node[below] at (A) {$A$};