Question

化简cosx-√3 cos(30°+x)+cos(x+60°)

Answer 1

和差化积公式cos α+cos β=2cos[(α+β)/2]·cos[(α-β)/2]

cosx-√3 cos(30°+x)+cos(x+60°)

=cosx+cos(x+60°) -√3 cos(30°+x)

=2cos(30°+x)cos(-30°)-√3 cos(30°+x)

=√3 cos(30°+x)-√3 cos(30°+x)

=0