a: góc BDC=180-60=120 độ

góc BOC=2*góc BAC=120 độ

góc BAD=góc CAD=60/2=30 độ

=>góc BOD=góc COD=60 độ

góc BOD=1/2*góc BOC

=>OD là phân giác của góc BOC

Xét ΔOBD có OB=OD và góc BOD=60 độ

nên ΔOBD đều

=>góc OBD=60 độ

Xét ΔOCD có OD=OC và góc DOC=60 độ

=>ΔOCD đều

=>góc OCD=60 độ

Xét tứ giác BOCD có

góc BOC=góc BDC

góc OBD=góc OCD

OB=OC

=>BOCD là hình thoi

b:

góc IBC+góc ICB=1/2(góc ABC+góc ACB)=1/2*120=60 độ

=>góc BIC=120 độ

góc BOC=góc BIC=120 độ

=>BOIC nội tiếp

xy=-11, x<y

x,y nguyên => \(\hept{\begin{cases}x=-11\\y=1\end{cases}}\)

Vậy (x;y)=(-11;1)

When a tropical storm reaches 120 kilometers per hour, it is called a typhoon

Wearing uniforms encourages students to be proud of being students of their school

the weather was snowy, we couldn't go to work yesterday
put the garbage into the dustbins, we will minimize pollution
so slowly that his students get bored
difficult to find a better solution

When a tropical storm reaches 120 kilometers per hour, it is called a typhoon

Wearing uniforms encourages students to be proud of being students of their school

the weather was snowy, we couldn't go to work yesterday
put the garbage into the dustbins, we will minimize pollution
so slowly that his students get bored
difficult to find a better solution

17 surprisingly

18 time-consuming

19 replacing

20 independent

21 qualifications

22 activists

The Internet provides us with a rich source of educational materials and courses.
Facebook has become very popular today because it makes communication around the world very easy
on working despite the rain
worked as a fashion designer for 2 years
I would join your family on the trip to your home village
schoolyard should be kept clean

1. B

2. C

3. C

4. B

5. A

6. D

7. C

8. C

9. A

10. B

1. B 2. C 3. C 4. B 5. A 6. D 7. C 8. C 9. A 10. B

Tớ ko giúp đc)): _{^{cọu tự tra google đuy,chứ có google để làm j ((:?}}