1.Составить во к следующим ответам.
1. I am doing my homework now.
2. They usually do their homework in the evening
3. My mother went shopping last Friday.
4. My friends have been in Italy 2 years ago.
2. Используйте глаголы в скобках в правильной форме.
1. I (has written, wrote, have written)
the letter yesterday.
2. Tamara (has, have) already (cleans, cleaned) the room.
3. I (have done, is doing, am doing) my lessons now.
4. He (has done, have done, did) his exercises till six o’clock.
Объяснение:
1.Составить во к следующим ответам.
1. I am doing my homework now.
2. They usually do their homework in the evening
3. My mother went shopping last Friday.
4. My friends have been in Italy 2 years ago.
2. Используйте глаголы в скобках в правильной форме.
1. I (has written, wrote, have written)
the letter yesterday.
2. Tamara (has, have) already (cleans, cleaned) the room.
3. I (have done, is doing, am doing) my lessons now.
4. He (has done, have done, did) his exercises till six o’clock.
sinx·cosx = -√3/4 потому что cos(-x) = cosx
1/2·sin2x = -√3/4 формула синуса двойного угла: sin2x = 2sinx·cosx
sin2x = -√3/2 умножили на 2 обе части
2x = (-1)^(n+1)·π/3 + πn , n∈Z
x = (-1)^(n+1)·π/6 + πn/2 , n∈Z - ответ
(-1)^(n+1) - это "минус единица в степени (n + 1)@
2sin(x/2)cos(x/2)+cos²(x/2)-sin²(x/2)-sin²(x/2)-cos²(x/2)=0
2sin(x/2)cos(x/2)-2sin²(x/2)=0
2sin(x/2)*(cos(x/2)-sin(x/2))=0
sin(x/2)=0⇒x/2=πn⇒x=2πn,n∈z
cos(x/2)-sin(x/2)=0/cos(x/2)
1-tg(x/2)=0
tg(x/2)=1⇒x/2=π/4+πk⇒x=π/2+2πk,k∈z
Объяснение:
