17. Δ CAD (∡D=90°) AVEM: sin DAC=co/ip sin 60°=CD/AC √3/2=CD/12√3 2CD=12(√3)² 2CD=36 CD=36/2=18 cm cos DAC=ca/ip cos 60°=AD/AC 1/2=AD/12√3 2AD=12√3 AD=12√3/2=6√3 CM ∡DAB=90°-60°=30° Δ ADB (∡D=90°) AVEM: cos DAB=ca/ip cos 30°=AD/AB √3/2=6√3/AB √3AB=12√3 AB=12√3/√3=12 cm sin DAB=co/ip sin 30°=DB/AB 1/2=DB/12 2DB=12 DB=12/2=6 cm BC=CD+DB BC=18+6=24 cm