Giúp mik với để mình dò lại bài mik ạ
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PN
2
HP
29 tháng 7 2021
\(\left|cosx\right|=\dfrac{1}{2}\)
\(\Leftrightarrow\left[{}\begin{matrix}cosx=\dfrac{1}{2}\\cosx=-\dfrac{1}{2}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\pm\dfrac{\pi}{3}+k2\pi\\x=\pm\dfrac{\pi}{2}+k2\pi\end{matrix}\right.\)
\(\Leftrightarrow x=\pm\dfrac{\pi}{3}+k2\pi\)
NV
Nguyễn Việt Lâm
Giáo viên
29 tháng 7 2021
\(\left|cosx\right|=\dfrac{1}{2}\)
\(\Leftrightarrow cos^2x=\dfrac{1}{4}\)
\(\Leftrightarrow\dfrac{1+cos2x}{2}=\dfrac{1}{4}\)
\(\Leftrightarrow cos2x=-\dfrac{1}{2}\)
\(\Rightarrow2x=\pm\dfrac{2\pi}{3}+k2\pi\)
\(\Rightarrow x=\pm\dfrac{\pi}{3}+k\pi\)
PN
1
DT
Đỗ Thanh Hải
CTVVIP
11 tháng 9 2021
Tham khảo
1. Someone will clean the room today. =>THE ROOM WILL BE CLEANED TODAY
2. Someone might steal the car. =>THE CAR MIGHT BE STOLEN
3. They had to cut down that tree.=>THAT TREE HAD TO BE CUT DOWN
4. They're going to demolish the old houses.=>THE OLD HOUSES ARE GOING TO BE DEMOLISHED
5. We can't restore the picture. =>THE PICTURE CAN'T BE RESTORED
6. You must make an appointment in advance.=>AN APPOINTMENT MUST BE MADE IN ADVANCE
7. I don't want people to make me a fool. =>I DON'T WANT TO BE MADE A FOOL
8. Someone has to look after the garden.=>THE GARDEN HAS TO BE LOOKED AFTER
9. He wants everybody to serve him. =>HE WANTS TO BE SERVED
10. They're going to interview him next week=>HE IS GOING TO BE INTERVIEWED NEXT WEEK
23 tháng 6 2023
5:
B=(x+y)^2-2xy
=225-2*(-100)=425
6:
a: C=(39+61)^2=100^2=10000
b: D=50^2-50^2+1=1
ND
0
Tham khảo
1. Someone will clean the room today. =>THE ROOM WILL BE CLEANED TODAY
2. Someone might steal the car. =>THE CAR MIGHT BE STOLEN
3. They had to cut down that tree.=>THAT TREE HAD TO BE CUT DOWN
4. They're going to demolish the old houses.=>THE OLD HOUSES ARE GOING TO BE DEMOLISHED
5. We can't restore the picture. =>THE PICTURE CAN'T BE RESTORED
6. You must make an appointment in advance.=>AN APPOINTMENT MUST BE MADE IN ADVANCE
7. I don't want people to make me a fool. =>I DON'T WANT TO BE MADE A FOOL
8. Someone has to look after the garden.=>THE GARDEN HAS TO BE LOOKED AFTER
9. He wants everybody to serve him. =>HE WANTS TO BE SERVED
10. They're going to interview him next week=>HE IS GOING TO BE INTERVIEWED NEXT WEEK