根号下(1-2sin10°cos10°)/[cos10°-根号下(1-sin^2 80°)]
=根号下(sin10°-cos10°)^2/[cos10°-根号下(cos^2 80°)]
=|sin10°-cos10°|/[cos10°-cos80°] cos10°>sin10°cos80°=sin10°
=(cos10°-sin10°)/(cos10°-sin10°)
=1