4 4 Put the verbs into the correct form, past simple or past continuous,
WHALE JUMPS ON SAILING BOAT!
Ralph Mothes and Paloma Werner (1)
(enjoy) a sailing trip
when a whale (2)
(jump) out of the sea and landed on their
boat.
They (3)
(sail) near Robben Island, South Africa when the
accident (4)
(happen).
Ralph and Paloma watched the whale swimming for about half an hour.
While they (5)
(watch), it went under the water and then
(6)
(come) up near the boat. Suddenly, it jumped out of the
water and landed on the boat. Then it (7)
(go) back into the sea.
While this (8)
(happen), someone in another boat filmed the
accident. (You can watch the video on YouTube®.)
Ralph and Paloma (9)
(be) able to take the boat back to the land.
ртпооаоаьмо вгаьвоьаьсsinx + cos x + sin2x = 1
sin x + cos x + 2sinx cosx -1=0
sin x + cos x +2sinx cosx -(sin²x+cos²x)=0
(sin x + cos x) + 2sinx cos x - (sin²x+cos²x+2sinx cosx -2sinx cos x)=0
(sin x+ cos x)+2sinx cosx - (sin x + cos x)² +2sinx cosx=0
(sin x + cos x)² + (sinx + cosx)+4sinxcosx=0
Пусть sin x + cos x = t причем (-√2 ≤ t ≤ √2), тогда возведем оба части до квадрата, имеем
(sin x + cos x)² = t²
1+2sinx cosx = t²
2sinxcosx = t²-1
Заменяем
t²+t+2*(t²-1)=0
t²+t+2t²-2=0
3t²+t-2=0
D=1+24 = 25
t1=(-1+5)/6=2/3
t2=(-1-5)/6 = -1
Возвращаем к замене
\begin{gathered}\sin x+\cos =-1\\ \sqrt{2} \sin(x+ \frac{\pi}{4} )=-1 \\ \sin(x+ \frac{\pi}{4} )=- \frac{1}{ \sqrt{2} } \\ x+ \frac{\pi}{4}=(-1)^{n+1} \frac{\pi}{4}+ \pi n,n \in Z\\ x=(-1)^{n+1} \frac{\pi}{4}- \frac{\pi}{4}+ \pi n,n \in Z\end{gathered}
sinx+cos=−1
2
sin(x+
4
π
)=−1
sin(x+
4
π
)=−
2
1
x+
4
π
=(−1)
n+1
4
π
+πn,n∈Z
x=(−1)
n+1
4
π
−
4
π
+πn,n∈Z
\begin{gathered}\sin x+\cos x= \frac{2}{3} \\ \sqrt{2} \sin(x+ \frac{\pi}{4})= \frac{2}{3} \\ \sin (x+ \frac{\pi}{4})= \frac{ \sqrt{2} }{3} \\ x=(-1)^n\arcsin( \frac{ \sqrt{2} }{3} )- \frac{\pi}{4}+ \pi n,n \in Z\end{gathered}
sinx+cosx=
3
2
2
sin(x+
4
π
)=
3
2
sin(x+
4
π
)=
3
2
x=(−1)
n
arcsin(
3
2
)−
4
π
+πn,n∈Z
Объяснение:
1
1 We haven't been reading books for a year.
2You haven't been runing very much lately.
3Jane hasn't been teaching English all year.
4Mark hasn't been doing exercise regularly
5Martin hasn't been eating regularly
2
1Every Monday Sally drives her kids to football practice.
2work/study
3starts
4don't swim/is
5agree
6talks
3
1 is Andrea swiming in the lake
2 is Martin washing his T-shirt?
3 are the guys carring the buckets?
4 is Peter holding the string of the kite?
4
1 is barking
2 are washing
3 are learning
5
1 don't play
6
1Where Joe does live? 2 Why don't they visit us? 3 When do we board the plane?
не знаю насколько правильно