GivenPQisparalleltoBCandPQdividestraingleABCintotwopartsTofindBPABoof:InΔAPQandΔABC∠APQ=∠ABC(AsPQisparalleltoBC)∠PAQ=∠BAC(Commonangles)soΔAPQ∼ΔABC(byAAsimilarity)Thereforear(ΔAPQ)ar(ΔABC)=AP2AB2⇒ar(ΔAPQ)2ar(ΔAPQ)=AP2AB2⇒12=AP2AB2⇒APAB−√12⇒(AB−BP)AB=1√2⇒1−BPAB=1√2⇒BPAB=1−1√2∴BPAB=√2−1√2