方法一样,逆用两角和与差的正弦公式
(1)
根号3sinx+cos x
=2[sinx*(√3/2)+cosx*(1/2)]
=2[sinx*cos(π/6)+cosx*sin(π/6)]
=2sin(x+π/6)
(2)
根号2(sin x - cos x);
=2[sinx*(√2/2)-cosx*(√2/2)]
=2[sinx*cos(π/4)-cosx*sin(π/4)]
=2sin(x-π/4)
(3)
根号2cos x -根号6sin x
=-2√2[sinx*(√3/2)-cosx*(1/2)]
=-2√2[sinx*cos(π/6)-cosx*sin(π/6)]
=-2√2sin(x-π/6)