您好!
1.sinC=sin(π-A-B)=sin(A+B)
sin(A-B)=3/5sin(A+B),5sin(A-B)=3sin(A+B)
5sinAcosB-5sinBcosA=3sinAcosB+3sinBcosA
2sinAcosB=8sinBcosA
tanA=4tanB
2.tan(A-B)=(tanA-tanB)/(1+tanAtanB)
=3tanB/(1+4tan^2B)
=3/(1/tanB + 4tanB)
1/tanB + 4tanB当tanB=1/2=0.5时,取得最小值,值为4
故tan(A-B)的最大值为3/4
如有疑问,请在线追问,随时为您解答.