в треугольнике АВС угол В-тупой, продолжение высот АА1, ВВ1, СС1 пересекаютя в точке О, угол АОС=60градусам. Найдите угол АВС.

определите, является ли треугольник АВС прямоугольным, если сумма его внешних углов при вершинах А и В равна 270 градусов .

напишите электролиз пожалуйста

ZnSO4

K2SiO3

Ca(OH)2

CuCl2 

помогите пожалуйста))) при каком натуральном значении x квадратный трёхчлен а)x^2+6x+5 принимает наименьшее значение б)-х^2+4x+1 принимает наибольшее значение?

Проверьте,пожалуйста мое письмо по английскому на наличие ошибок! (письмо Wendy) ...Yesterday we had School Science Week.Do you have such an event at your school ? What kind of events do you have and what are they about ? How do you prepare for them? ...yesterday i took my younger sister to the Zoo ask 3 questions her visit to the Zoo. Мое письмо Dear Wendy, Thank you for your lovely letter.I was awfully glad to wrote it, I havr not written sooner as I wanted to invate you round and would never find a suitable time. In your last letter you asked me about Science Week in my school.Every year we have week of foreign languages.These days we prepare for song and creative competitions.We read poems and sing songs in German,English and other languages.I like to take part in these competitions.They are very interasting also help to open talents of children. Last time you said someyhing about your walk with younger sister to the Zoo.Did you like the Zoo?What were you doing there? Was you sister delighted? Do come if you can. Yours, Lera.