(1)在Rt△ABC中,∠B=90°根据勾股定理得:AC= AB2+BC2 ,= 82+62 ,=10;(2)在△ACD中∵AC2+CD2=102+242=262=DA2,∴△ACD是直角三角形,∠ACD=90°,∴S四边形ABCD=SRt△ABC+SRt△ACD,= 1 2 ×AB×BC+ 1 2 ×AC×CD= 1 2 ×8×6+ 1 2 ×10×24=24+120=144.