∵在△ABC中，若tanAtanB＝2c−bb，根据正弦定理得 sinAcosBcosAsinB=2sinC−sinBsinB．化简可得sinAcosB+sinBcosA=2sinCcosA，∴sin（A+B）=2sinCcosA，∴sinC=2sinCcosA，∴cosA=12，∴A=60°，故答案为：60°．...