已知：tan(a-b)=sin2a/(5-coa2b),求证2tana=3tanb

已知：tan(a-b)=sin2a/(5-coa2b),求证2tana=3tanb
已知：tan(a-b)=sin2a/(5-coa2b),求证2tana=3tanb

已知：tan(a-b)=sin2a/(5-coa2b),求证2tana=3tanb
利用1+(tanx)^2=1/(cosx)^2 进行化简：
(tanA)＾2=2*(tanB)＾2 +1
[1/(cosA)^2]-1=[2/(cosB)^2]-1
2(cosA)^2=(cosB)^2
2[1-(sinA)^2]=1-(sinB)^2
2-2(sinA)^2=1-(sinB)^2
(sinB)＾2=2(sinA)＾2 -1