原式=sin10°/cos10° + 1/sin40°
=sin10°/sin80° + 1/sin40°
=sin10°/2sin40°cos40° + 2cos40°/2sin40°cos40°
=(sin10°+ 2cos40°)/2sin40°cos40°
=(sin10°+ 2cos40°)/sin80°
=(sin10°+ 2cos40°)/cos10°
=【sin10°+ 2cos(30°+10°)】/cos10°
=二倍根号三cos10°/cos10°
=二倍根号三
原式=sin10°/cos10° + 1/sin40°
=sin10°/sin80° + 1/sin40°
=sin10°/2sin40°cos40° + 2cos40°/2sin40°cos40°
=(sin10°+ 2cos40°)/2sin40°cos40°
=(sin10°+ 2cos40°)/sin80°
=(sin10°+ 2cos40°)/cos10°
=【sin10°+ 2cos(30°+10°)】/cos10°
=二倍根号三cos10°/cos10°
=二倍根号三