In a right triangle ΔABC with right angle at B, BD is a perpendicular, dropped onto the hypotenuse. If AC = 2AB, what is the area of Δ ABD, given, area of Δ ABC = 5 sq units.
1.25 sq. unit
Given,ABAC=12 and Ar(ΔABC)=5 sq.unitsConsiderΔABD and ΔABC:∠BAD=∠BAC−−−−[commom angle]∠BDA=∠ABC−−−−[90∘]By AA similarity criterion,ΔABD∼ΔABCHence,Ar(ΔABD)Ar(ΔABC)=(ABAC)2=(12)2=14i.e.,Ar(ΔABD)×4=Ar(ΔACB)⇒Ar(ΔABD)=54=1.25 sq.unitsHence the area of ΔABD is 1.25 sq.units