tan2α=-4/3则tanα=?

tan2α=-4/3则tanα=?
tan2α=-4/3则tanα=?

tan2α=-4/3则tanα=?
tan2a=2tana/(1-tan²a)
令tana=t
所以
2t/(1-t²)=-4/3
3t=-2+2t²
2t²-3t-2=0
(2t+1)(t-2)=0
t=-1/2或t=2
所以tana=-1/2或2

tan2α=-4/3=2tanα/1-tan²α
∴2tan²α-3tanα-2=0
∴(tanα-2)(2tanα+1)=0
解得：tanα=2或-1/2

-1/2或2