A={y>0},B={y<1/2}
y=log2x,当x>1时,log2x>log2(1)=0,即y>0
y=(1/2)^x,当x>1时,(1/2)^x<(1/2)^1=1/2,即y<1/2
所以A∩B={y|0＜y＜1/2}