∵AB是圆O的直径∴∠ACB＝∠ADB＝90∴BC＝√（AB²-AC²）＝√（36-4）＝4√2∴S△ABC＝AC×BC/2＝2×4√2/2＝4√2∵CD平分∠ACB∴∠ACD＝∠ACB/2＝45∵∠ACD、∠ABD所对应圆弧都为劣弧AD∴∠ABD＝∠ACD＝45...