〔cos40°(cos10°+√3sin10°)〕/ （2cos^25°-1）
=[cos40°(cos10°+√3sin10°)]/ cos50°
=[2cos40°(1/2*cos10°+√3/2*sin10°)]/ cos50°
=[2cos40°(sin30°*cos10°+cos30°*sin10°)]/ cos50°
=[2cos40°*sin(30°+10°)]/ cos50°
=[2cos40°*sin40°]/ cos50°
=sin80°/ cos50°
=sin(180°-100°)/ cos50°
=sin100°/ cos50°
=2sin50°cos50°/cos50°
=2sin50°