tan2a=2tana/(1-tan²a)=2/3/(1-1/9)=2/3*9/8=3/4
tan(2a-b)
=(tan2a-tanb)/(1+tan2atanb)
=(3/4+1/7)/(1-1/7*3/4)
=25/28/(25/28)
=1
2a-b=π/4+kπ k∈z
tan2a=2tana/(1-tan²a)=2/3/(1-1/9)=2/3*9/8=3/4
tan(2a-b)
=(tan2a-tanb)/(1+tan2atanb)
=(3/4+1/7)/(1-1/7*3/4)
=25/28/(25/28)
=1
2a-b=π/4+kπ k∈z