Котангенс тройного угла

\[\mathrm{ctg}{3 \alpha} = \frac{\mathrm{ctg^3}{\alpha} - 3 \mathrm{ctg}{\alpha}}{3 \mathrm{ctg^2}{\alpha} - 1}\]

\[\sin{3 \alpha} = 3 \sin{\alpha} - 4 \sin^3 {\alpha}\]

\[\cos{3 \alpha} = 4 \cos^3 {\alpha} - 3 \cos{\alpha}\]

\[\mathrm{tg}{3 \alpha} = \frac{3 \mathrm{tg}{\alpha} - \mathrm{tg^3}{\alpha}}{1 - 3 \mathrm{tg^2}{\alpha}}\]