左边=sin(60°+α)cos(60°-α)+sin(60°+α)cos(60°-α)
=[sin(60°+α)cos(60°-α)+cos(60°+α)sin(60°-α)]+[sin(60°+α)cos(60°-α)-cos(60°+α)sin(60°-α)]
=sin[(60°+α)+(60°-α)]+sin[(60°+α)-(60°-α)]
=sin120°+sin2α
=√3/2+sin2α
=右边 .