ABC is triangle, right angled at A. The resultant of the forces acting along AB, AC ???? ???? with magnitudes 1 AB and 1 AC respectively is the force along AD ???? , where D is the foot of the perpendicular from A onto BC. The magnitude of the resultant is (1) (AB)(AC) AB + AC (2) 1 1 AB AC + (3) 1 AD (4) ( ) ( ) 2 2 2 2 AB AC AB AC