Помогите срочно а то мама убьет

В электрической цепи ток и напряжение меняются по законам I = 50 cos l00(пt) (A), U = 30 cos(100 пt + п/3) (В). Найдите мощность выделяемую в цепи. Там формула P=IU\2. Как пойти к этой формуле?Можно пожалуйста с подробным объяснением)

Change the following affirmative sentences into

negative ones. (Give different versions where possible.)

1. Some of the students have already passed the exam.

2. It

was so unexpected and unusual.

3. There was some hesitation in her eyes.

4. But he did tell the truth after all.

5. The situation will

change for the better.

6. I was puzzled by many things.

7. It was

to happen some day.

8. There are lots of things to add.

9. The article will lose its significance by that time.

10. I will tell you

everything some day.