√(1-2sin40°cos40°)/[cos40°-√{1-(sin50°)^2]}
=√(sin40°-cos40°)^2/[cos40°-√(coc50°)^2]
=(cos40°-sin40°)/(cos40°-coc50°) cos40°>sin40°
=(cos40°-sin40°)/(cos40°-sin40°)
=1