(tan20-根号3)/sin20
=(sin20/cos20-sin60/cos60)/sin20
=(sin20*cos60-sin60*cos20)/cos60/cos20/sin20
=-sin40/cos60/cos20/sin20
=-2sin20*cos20/cos60/cos20/sin20
=-4
(tan20-根号3)/sin20
=(sin20/cos20-sin60/cos60)/sin20
=(sin20*cos60-sin60*cos20)/cos60/cos20/sin20
=-sin40/cos60/cos20/sin20
=-2sin20*cos20/cos60/cos20/sin20
=-4