Kto znayes etot ? pojalustaa pomogite

[latex]tg2 \alpha = \frac{2*tg \alpha }{1- tg^{2} \alpha } [/latex] [latex] \frac{2}{ \frac{1}{tg \frac{ \pi }{8} }-tg \frac{ \pi }{8} } =2:( \frac{1- tg^{2} \frac{ \pi }{8} }{tg \frac{ \pi }{8} } )= \frac{2*tg \frac{ \pi }{8} }{1- tg^{2} \frac{ \pi }{8} } =tg(2* \frac{ \pi }{8} )=tg \frac{ \pi }{4}=1 [/latex]