原式=sin40*(tan10-tan60)
=sin40(sin10/cos10-sin60/cos60)
=sin40(sin10cos60-cos10sin60)/(cos10cos60)
=sin40*(-sin50/(sin80sin30))
=-sin40cos40/(2sis40cos40*1/2)
=-1
原式=sin40*(tan10-tan60)
=sin40(sin10/cos10-sin60/cos60)
=sin40(sin10cos60-cos10sin60)/(cos10cos60)
=sin40*(-sin50/(sin80sin30))
=-sin40cos40/(2sis40cos40*1/2)
=-1