1.已知tana=1/3,tanb=-1/4求tan(2a-2b).2.已知sin(a+π/6)=1/3求sin(π/6-2a)

1.由 tan(α－β)＝(tanα－tanβ)/(1＋tanα•tanβ)和tan2A=2tanA/(1－tan2A),得tan(2a-2b)=(tan2a-tan2b)/(1+tan2a tan2b)=[2tana/(1-tan²a)-2tanb/(1-tan²b)]/{1+4tana tanb/[(1-tan²a)(1-t...