1) \(\displaystyle{ tg x + ctg x +tg 3x+ ctg 3x= \frac{8 cos^{2}2x }{sin 6x}}\)
2) \(\displaystyle{ \frac{sin( \frac{ \pi }{2}+3 \alpha ) }{1-sin(3 \alpha - \pi )} =ctg( \frac{5}{4} \pi + \frac{3}{2} \alpha)}\)
3) \(\displaystyle{ sin 2 \alpha (1+tg2 \alpha tg \alpha ) + \frac{1+sin \alpha }{1-sin \alpha }=tg 2 \alpha + tg^{2}( \frac{ \pi }{4}+ \frac{ \alpha }{2} )}\)