tan(π+2a)=-4/3 ===> tan2a=-4/3tan2a=2tana/(1-tan^2 a)=-4/3===> -3tana=2-2tan^2 a===> 2tan^2 a-3tana-2=0===> (2tana+1)(tana-2)=0===> tana=-1/2,或者tana=2因为a是第二象限角,则tana＜0所以,tana=-1/2...