y=2sin2B+sin(2B+π/6)
=2sin2B+sin2Bcos(π/6)+sin(π/6)cos2B
=(2+√3/2)sin2B+(1/2)cos2B
(2+√3/2)^2+(1/2)^2=4+1+2√3=5+2√3
设sinu=(1/2)/√(5+2√3) cosu=(2+√3/2)/√(5+2√3)
y=√(5+2√3)*sin(2B+u)
2B+u=90时
y最大值√(5+2√3)
2
cos(A-C)/21 B>π/4时
tanB>cos[(A-C)/2]
sinB>cos[(A-C)/2]sin[(A+C)/2]
2sinB>sinA+sinC
2b>a+c