Задача 12498 tg^3x-tg^3y/(1+tgx*tgy)*(tg^2x+tgx*tgy+tg^2y)...

mari_nuzhnaya

23.12.2016

tg^3x-tg^3y/(1+tgx*tgy)*(tg^2x+tgx*tgy+tg^2y)

SOVA

23.12.2016

★

(tg^3x–tg^3y)/((1+tgx·tgy)·(tg^2x+tgx·tgy+tg^2y))=
=((tgx-tgy)*(tg^2x+tgx·tgy+tg^2y))/((1+tgx·tgy)·(tg^2x+tgx·tgy+tg^2y))=
=(tgx-tgy)/(1+tgx·tgy)=
=tg(x-y)