Sửa Latex:

\(\text{Δ φ}=\dfrac{\text{2 π d}}{\text{λ}}=\dfrac{\text{π}}{2}\Rightarrow d=\dfrac{\text{λ}}{4}10cm\)

Ta có:

\(\dfrac{2\text{π }x}{\text{λ}}=2\text{π}.0,025x\Rightarrow\text{λ}=40cm \)

\(\text{Δ φ}=\dfrac{2\text{π}d}{\text{λ}}=\dfrac{\text{\text{π}}}{2}\Rightarrow d=\dfrac{\text{λ}}{4}=10cm\)

Chu kỳ dao động:

\(T=2\text{π }\sqrt{\dfrac{l_1+l_2}{g}}\Rightarrow T^2=\left(2\text{π }\right)^2=\dfrac{l_1+l_2}{g}=T^2_1+T_2^2\)

\(T'=2\text{π }\sqrt{\dfrac{l_1-l_2}{g}}\Rightarrow T'^2=\left(2\text{π }\right)^2\dfrac{l_1-l_2}{g}=T^2_1-T^2_2\)

\(\Rightarrow\left\{{}\begin{matrix}T^2_1+T^2_2=2,7^2\\T^2_1-T_2^2=0,9^2\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}T_1=2s\\T_2=1,8s\end{matrix}\right.\)

1. Tần số của dòng điện bằng tần số điện áp:

\(f=\dfrac{\text{ω}}{2\text{π}}=50Hz\)

2. Cường độ hiệu dụng dòng điện:

\(I=\dfrac{I_0}{\sqrt{2}}=\dfrac{4}{\sqrt{2}}=2\sqrt{2}A\)

a/ 

Program baitap;

Uses crt;

Begin

Clrscr;

Writeln('Dien tich HCN:', 4*5);

Writeln('Chu vi HCN:', (4+5)*2);

Readln

End.

b/

Program baitap;

Uses crt;

Var a,b:real;

Begin

Clrscr;

Write('Nhap chieu dai va chieu rong:');

Readln(a,b);

Writeln('Dien tich HCN:', a*b);

Writeln('Chu vi HCN:', (a+b)*2);

Readln

End.

1:

Program baitap1;

Uses crt;

Var A:array[1..200] of integer;

      S,i:integer;

Begin

Clrscr;

S:=0;

For i:=1 to 10 do

     Begin

     Write('A[',i,']=');

     Readln(A[i]);

     If (A[i] mod 2=1) then S:=S+A[i];

     End;

Writeln('Tong cac phan tu co gia tri le:',S);

Readln

2:

Program baitap2;

Uses crt;

Var A:array[1..200] of integer;

      S,i:integer;

Begin

Clrscr;

S:=0;

For i:=1 to 15 do

     Begin

     Write('A[',i,']=');

     Readln(A[i]);

     If (A[i] mod 2=0) then S:=S+A[i];

     End;

Writeln('Tong cac phan tu co gia tri chan:',S);

Readln

End.

End.

1. D

2. D

1. has already watched

2. Has he written

3. have travelled

4.haven't given

5.hasn't seen 

6.have been

7.has rained 

8.hasn't had 

9.hasn't played 

10.have you known 

11. Have you taken 

12.Has she eat 

13.has lost 

14.have - left - has left 

15.have walked 

16.hasn't came 

17.Have - been 

18.has been 

16. C

17. B

18. C

19. D

20. B

I.

1. D

2. A

3. C

4. D

5. C

II.

6. C

7. D

8. C

9. C

10. D