ctgx = (ctg^2(x/2)-1)/(2*ctg(x/2))из равенства найти ctg(x/2), а tg(x/2) = 1/ctg(x/2)
caviar.many people think that caviar is the national food of russia people. caviar has become very excpensive now.Pancakes.some people eat pancakes with caviar, some of them like pancakes with honey or sour cream.honey.it is national food of russia too, especially it is loved our brown bears.
икра.многие люди думают что икра это национальная еда россиян.икра сейчас стала очень дорогой.блины.некоторые люди едят блины с икрой, некоторые из них любят блины с медом или сметаной. мед. это тоже национальная еда россиян, особенно его любят наши бурые мишки.
supposed she (to like) the hotel. 7. i am afraid they (not to come) yet. 8. he wanted to know if the station (to be) far away. 9. eric doesn't know who (to phone) him at five o'clock. 10. he admitted he (not to be) here for weeks. 11. she was sorry she (to arrive) so late. 12. jean promised she never (to speak) to me again. 13. andy said he just (to buy) a new car. 14. my mother decided
that she never (to drink) coffee late at night. 15. i hear you already (to find) a new job. 16. we were sure our children (to sleep). 17. i didn't think they still (to discuss) that problem. 18. it is remarkable that you (to come) at last. 19. my doctor thinks i (to be) allergic to pineapples. 20. sophia knew her aunt (to be) glad to visit her in two days.