tg(a) = ? если 45 sin^2(a)+11 cos^2(a)=20 и (a)принадлежит(п/2;п)

 Complete the sentences with the correct forms of the verbs in brackets.

Once a philosopher was travelling down the river in a small boat. While he 1 (cross) the river he 2 (ask) the boatman: ” 3 you ever (hear) about Philosophy?” “No,” 4 (say) the boatman. “I 5 never (hear) about it. What 6 (be) it?” “I 7 (be) sorry for you, indeed,” replied the learned man, “you 8 (lose) a quarter of your life as it’s a very interesting science!”
Several minutes later the philosopher asked the boatman another question: “9 you (hear) about Astronomy, when you 10 (be) at school?” “No, I 11 (leave)school many years ago and I 12 (forget) all about it,” was the answer. To this the philosopher answered that he 13 (be) really sorry for the man, and he 14 (think) that the boatman 15 (lose) a second quarter of his life.
Some minutes passed and the passenger again 16 (wonder) if the man ever 17 (hear) about Algebra. And the man 18 (have to) admit that he 19 never (know) anything about it. “In that case you certainly 20 (lose) a third quarter of your life!” said the scientist.
At that moment the boat 21 (strike) on a big stone. The boatman jumped and 22 (cry):”23 you ever (learn) 24 (swim)?” “No,” was the answer. The boatman explained sadly to the philosopher that he 25 (be) sure the scientist 26 (lose) his whole life as the boat 27 (sink).

из лекарственных трав - шалфея, ромашки и валерианы - составили сбор, взяв их в отношения 2:5:3 Какой % этого сбора составляет каждая из трав?

a^2-b^2-a-b  решите пжлст

материк с наиболее изрезанной береговой линией