原式=4sin40°-sin40°/cos40°
=(2sin80°-sin40°)/cos40°
=(sin80°+sin80°-sin40°)/cos40°
=(sin80°+2cos60°sin20°)/cos40°
=(sin80°+sin20°)/cos40°
=2sin50°cos30°/cos40°
=√3
原式=4sin40°-sin40°/cos40°
=(2sin80°-sin40°)/cos40°
=(sin80°+sin80°-sin40°)/cos40°
=(sin80°+2cos60°sin20°)/cos40°
=(sin80°+sin20°)/cos40°
=2sin50°cos30°/cos40°
=√3