解:作CD垂直射线BA于D,∠B=45度,则CD=BD,CD=(√2/2)BC=√6/2.AD=√(AC^2-CD^2)=√2/2=AC/2,则∠ACD=30度.当∠BAC为锐角时:∠ACB=∠ACD+∠BCD=75度;当∠BAC为钝角时:∠ACB=∠BCD-∠ACD=45度-30度=15度.
sinB : b= sinA: asinA=√3 /2A=60°A+B+C=180°C=75°
