sin70(1-√3tan50)
=sin70[1-(√3sin50/cos50)]
=sin70[(cos50)-√3sin50)/cos50]
=2sin70[(1/2)cos50-(√3/2)sin50)/cos50]
=2sin70[cos60cos50-sin60sin50)/cos50]
=2sin70cos(60+50)/cos50
=-2cos20sin20/cos50=-1
sin70(1-√3tan50)
=sin70[1-(√3sin50/cos50)]
=sin70[(cos50)-√3sin50)/cos50]
=2sin70[(1/2)cos50-(√3/2)sin50)/cos50]
=2sin70[cos60cos50-sin60sin50)/cos50]
=2sin70cos(60+50)/cos50
=-2cos20sin20/cos50=-1