解析：∵a、b、c,成等比数列∴b^2=ac∵cosB=(a^2+c^2-b^2)/2ac=(a^2+c^2-ac)/2ac≥(2ac-ac)/2ac=1/2即cosB≥1/2,∴0＜B≤60°,45°＜B+45°≤105°∵sinB+cosB=√2sin(B+45°）∴1＜√2sin(B+45°）≤√2y=sinB+conB...