tan(2x-π/4),x∈[0,π/3]
(2x-π/4)∈[-π/4,5π/12]
对于tany,在y∈[-π/4,5π/12]时,是连续的、且是单调的.
tan(-π/4)=-1,tan(5π/12)=2+√3
即：tan(2x-π/4)∈[-1,2+√3]