│2a-b│=√((2cosA-√3)²+(2sinA-1)²)=√(数察(2cosA)²-4√3cosA+(2sinA)²-4sinA+4)=√(戚旅8-4√3cosA-4sinA)=2√(1-(sin π/3cosA+cosπ/3sinA))=2√(1-sin(π/3+A)高毕凳)
最小值=1-sin(π/3+A)=0
解:
2a-b=(2cosA-√3,2sinA-1)
|2a-b|=√(2cosA-√3)^2+(2sinA-1)^2 =√(4-4√3cosA+3-4sinA+1)
=√(8-(4√旦答3cosA+4sinA)) =√(8-8sin(A+π/启历3))
|2a-b|模旁慧min =√(8-8)=0
8-4(根号3)