解由C=90°,即A+B=90°故a=csinA,b=csinB=ccosA故（a+b）/c=（csinA+ccosA)/c=sinA+cosA=√2sin（A+π/4)由A属于（0,π/2)即A+π/4属于（π/4,3π/4)即√2/2＜sin（A+π/4)≤1即1＜√2sin（A+π/4)≤√2即1＜（a+b）...