tan(A+B) = (tanA+tanB)/(1-tanAtanB) tan(b-∏/4)=(tanb-tan∏/4)/(1+tanbtan∏/4)1/4 =(tanb-1)/(1+tanb)4(tanb-1)=1+tanb3tanb=5tanb=5/3tan(a+b)=(tana+tanb)/(1-tanatanb)2/5=(tana+5/3)/(1-5/3*tana)5(tana+5/...采纳一下吧！或 tan(b-45度)=1/4
(tanb-1)/(1+tanb)=1/4 得tanb=5/3

tan(a+b)=2/5
(tana+tanb)/(1-tanatanb)=2/5
代入tanb=5/3 得tana=-19/25

tan(a+45度)=(tana+1)/(1-tana)=3/22