[질문] 삼각함수배각공식알려죠요

1.sin2θ=2sinθcosθ 2.cos2θ=cos^2θ-sin^2θ=2cos^2θ-1 =1-2sin^2θ 2tanθ 3.tan2θ= 1-tan^2θ 3배각공식은 cos3x=4cos^3xㅡ3cosx sin3x=3sinxㅡ4sin^3x