已知tana/tana-1=-1,求sin²a+sinacosa+2的值?

问题描述:

已知tana/tana-1=-1,求sin²a+sinacosa+2的值?

tana/(tana-1)=-1,tana=1/2sin²a+sinacosa+2=(sin²a+sinacosa)/1+2=(sin²a+sinacosa)/(sin^2a+cos^2a)+2 (上下同除以cos^2a)=(tan^2a+tana)/(tan^2a+1)+2=3/5+2=13/5