Question

tana=2 a 为锐角.求tan a/2

Answer 1

α/2为锐角,tan(α/2)>0

tan（α）=2tan(α/2) / {[1-tan(α/2)]^2}

设tan(α/2)=x

x^2+x-1=0

x=(根号5)/2-1/2=tan(α/2)