\(\cos(3x) = \cos^2(x) \cdot \cos(x) - \sin^2(x) \cdot \sin(x)\)

\(\cos(3x) = \cos(2x) \cdot \cos(x) - \sin(2x) \cdot \sin(x)\)

\(\cos(3x) = \cos(2x) \cdot \sin(x) + \sin(2x) \cdot \cos(x)\)

\(\cos(3x) = \cos^2(x) \cdot \sin(x) + \sin^2(x) \cdot \cos(x)\)