sin40(tan10-√3）
=sin40(sin10/cos10-√3cos10/cos10)
=sin40[(sin10-√3cos10)/cos10]
sin10-√3cos10
=2(1/2sin10-√3/2cos10)
=2(sin10cos60-cos10sin60)
=2sin(10-60)
=-2sin50
sin40[(sin10-√3cos10)/cos10]
=sin40*(-2sin50)/cos10
=-2sin40cos40/cos10
=-sin80/cos10
=-cos10/cos10
=-1