Составьте структурную формулу пропановой кислоты

Люди помогите очень срочно нужно, выручайте пожалуйста "Вычислите 3sin a - cos a если известно что cos 2a = -1/2 ; п < 2a < 3п/2 (см. внутри варианты решения) Заранее спасибо. Оставлю отзывы и благодарность на странице решившего 

В каком слове правописание суффикса определяется тем, что образовано от глагола первого спряжения?

1.складывалась

2.бороющихся

3. любимых

4.доходчиво

Текст Yesterday was Friday. The weather was fine. Bill and Taras walked in the streets and visited some places of interest. Bill`s parents were at work. So Kate cooked the dinner. Bill and Taras helped her. After dinner they cleaned the rooms and washed the plates. Then Kate listened to music and phoned her friends. Bill and Taras played computer games with Nick and Vicky. In the evening Taras and the Browns watched TV. The film was very interesting and Taras liked it a lot. Задание к тексту : Answer What day was yesterday? Was the weather fine or bad? Were the boys at home in the morning? Where were Bills parents in the daytime? Was Kate in? Where were the Browns yesterday evening? Can you say what the film was about?