sin(3α) = 3sinα-4sin^3α = 4sinα·sin(60°+α)sin(60°-α) cos要令垂标浓简挥找诉规创(3α) = 4cos^3α-3cosα = 4cosα·cos(60°+α)cos(60°-α) tan(3α) = (3tanα-tan^3α)/(1-3tan^2α) = tanαtan(π/3+α)tan(π/3-α)