选C.1/（a^2)+1/(b^2)≥1设：90°>x>0,tanx=sinx/cosx=a/bbsinx=acosxb^2*sin^2x=a^2*cos^2xb^2*(1-cos^x)=a^2*cos^2xcosx=√[b^2/(a^2+b^2)]已知x/a+y/b=1经过点（cosa,sina),则cosa/a+sina/b=1cosa+(a/b)*sina=aco...