AB/AC=3/7 ⇒ AB=3AC/7
ADxBC=ACxAB ⇒ AD=ACxAB/BC
42=(ACx3AC/7)/BC
42=3AC²/7BC ⇒ BC=AC²/98 (a)
BC²=AC²+AB²=AC²+(3AC/7)²=(49AC²+9AC²)/49=58AC²/49
BC=√58AC²/49=AC√58/7 (b)
egalam a cu b
AC²/98=AC√58/7 cm
AC/98=√58/7 cm
AC=98x√58/7=14√58 cm
AB=3/7 × 14√58=6√58 cm
BC=AC√58/7=14√58×√58/7=116 cm
CD=√(14√58)²-42²)=√(11368-1764) =√9604=98 cm
DB=BC-CD=116-98=18 cm