Найдите площадь ромба, если его высота равна 13см, а острый угол 30 градуов. 

Упр. 286. Раскройте скобки, выбирая требую­щееся время глагола.

1. Не said he (is staying, was staying) at the "Ritz" Hotel. 2. They realized that they (lost, had lost) their way in the dark. 3. He asked me where I (study, studied). 4. I thought that I (shall finish, should finish) my work at that time. 5 He says he (works, worked) at school two years ago. 6. Victor said he (is, was) very busy. 8. My friend asked me who (is playing, was playing) the piano in the sit­ting-room. 9. He said he (will come, would come) to the station to see me off. 10. I was sure he (posted, had posted) the letter. 11. I think the weather (will be, would be) fine next week. I hope it (will not change, would not change) for the worse. 12. I knew that he (is, was) a very clever man. 13.1 want to know what he (has bought, had bought) for her birthday. 14. I asked my sister to tell me what she (has seen, had seen) at the museum.