B(NGHĨ.LÀ.THẾ)

Xét tam giác ABC có: góc A+góc B+góc C=180^o

=>Góc B+góc C=180^o-góc A=180^o-60^o=120^o

Tổng tia phân giác của góc B và góc C là (góc B)/2+(góc C)/2

=(góc B+góc C)/2=120^o/2=60^o=>góc IBC+góc ICB=60^o

Xét tam giác BIC có: góc IBC+góc ICB+góc BIC=180^o

=>Góc BIC=180^o-(góc IBC+góc ICB)=180^o-60^o=120^o

Vậy góc BIC=60^o

Góc BIC+60^o=>chọn D

PTHH: 2Al + 6HCl → 2AlCl₃ + 3H₂

PTHH: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O

PTHH: Fe₂O₃ + 6HCl → 2FeCl₃ + 3H₂O

PTHH: K₂O + 2HCl → 2KCl + H₂O

Lần sau em đăng câu hỏi đúng box để mọi người hỗ trợ nha

PTHH: 2Al + 6HCl → 2AlCl₃ + 3H₂

PTHH: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O

PTHH: Fe₂O₃ + 6HCl → 2FeCl₃ + 3H₂O

PTHH: K₂O + 2HCl → 2KCl + H₂O

lỗi r nha bn

lỗi

a: Xét ΔAMC và ΔBMD có 

MA=MB

\(\widehat{AMC}=\widehat{BMD}\)

MC=MD

Do đó: ΔAMC=ΔBMD

\(1,\\ a,=\dfrac{\left(3+2\sqrt{3}\right)\sqrt{3}}{3}+\dfrac{\left(2+\sqrt{2}\right)\left(\sqrt{2}-1\right)}{1}\\ =\dfrac{3\sqrt{3}+6}{3}+\sqrt{2}=\sqrt{3}+1+\sqrt{2}\\ b,=\left(\dfrac{\sqrt{5}+\sqrt{2}}{3}-\dfrac{\sqrt{5}-\sqrt{2}}{3}+1\right)\cdot\dfrac{1}{\left(\sqrt{2}+1\right)^2}\\ =\dfrac{\sqrt{5}+\sqrt{2}-\sqrt{5}+\sqrt{2}+3}{3}\cdot\dfrac{1}{\left(\sqrt{2}+1\right)^2}\\ =\dfrac{2\sqrt{2}+3}{3\left(3+2\sqrt{2}\right)}=\dfrac{1}{3}\)

\(2,\\ A=2x+\sqrt{\left(x-3\right)^2}=2x+\left|x-3\right|\\ =2\left(-5\right)+\left|-5-3\right|=-10+8=-2\\ B=\dfrac{\sqrt{\left(2x+1\right)^2}}{\left(x-4\right)\left(x+4\right)}\left(x-4\right)^2=\dfrac{\left|2x+1\right|\left(x-4\right)}{x+4}\\ B=\dfrac{17\cdot4}{12}=\dfrac{17}{3}\)

1 hadn't seen - were

2 doesn't like - being phoned

3 is eaten

4 is leaving - will wait

5 won't be - will you go

6 is coming - don't want

7 hasn't read - have gone

8 haven't seen - left

9 was washing - was writing

10 sets - goes

11 were talking - walked

12 has stayed - studied - was

13 was made

14 had told - went away

15 will be held

16 had gone - sat - rested

17 watched - had done

hình bé quá

sin 65⁰=cos 35⁰
\(cos70^0=sin30^0\)
\(tan80^0=cot20^0\)
\(cot68^0=tan32^0\)

Ko nhìn chữ bn ơi, bn cho to hình một tý