A) vì ΔABC là Δ vuông tại A nên \(\widehat{A}=90^0\)

số đo của \(\widehat{C}\) là: \(\widehat{B}+\widehat{C}=\widehat{A}\Rightarrow\widehat{C}=\widehat{A}-\widehat{B}=90^0-60^0=30^0\)

TA CÓ: \(\widehat{A}>\widehat{B}>\widehat{C}\)

\(\Rightarrow BC>AC>AB\)

b) xét Δ vuông ABE và Δ vuông HBE, có:

\(\widehat{ABE}=\widehat{HBE}\left(gt\right)\)

BE là cạnh chung

⇒ ΔABE = ΔHBE (ch-gn)

⇒ AB = BH (2 cạnh tương ứng)

xét ΔABH có: AB = BH (cmt)

⇒ ΔABH là Δ cân

đổi 2,2m = 22dm

thể tích của khối gỗ là:

22 x 5 x 3 = 330 (dm³)

khối lượng của khối gỗ đó là:

330 x 0,6 = 198 (kg)

1 How beautiful the Christmas tree is
2 My sister wasn't able to swim last year
3 How heavy were you two years ago
4 The road is 10 miles in length
5 He is 5 feet tall
6 The dictionary has a thickness of 5 inches
7 What is the breadth of the window
8 I think learning English well is not easy
9 What is the matter with you
10 How high is the Big Ben Clock Tower
11 How much does your son weigh
12 What is the price of this face mask
13 What is the length of the Mekong River
14 What is the width of West Lake
15 How old is your son
16 Where do you live
17 How deep is the Pacific Ocean
18 I will cook dinner tonight
19 Don't forget to wake me up at 6.30 tomorrow morning
20 What is the thickness of that novel
21 What a lovely dinner it is
22 He doesn't live close to the school
23 Long is a very good swimmer
24 My brother is a slow cyclist
25 Mr. Cuong is skilled at playing tennis
26 Mrs. Chi types quickly
27 Thoa sings smoothly
28 Miss An is a fast runner
29 Mr. Hung is a safe driver
30 Minh's sister dances marvelously
31 Mrs. Oanh cooks well
32 Khanh is a fluent English speaker
33 You don't have to finish the work today
34 Both I and my brother like roller skating
35 What is the cost of these rackets
36 Zidane is one of the greatest football players in the world
37 The little fish were the most beautiful
38 Why didn't you attend class last Monday
39 Because of her sickness, Lan didn't go to school yesterday
40 You had better not eat too much meat
41 What is the weight of the chicken
42 How tall was Peter last year
43 It's usually sunny during summer days
44 If you don't work hard, you will fail the exam
45 It takes two hours to get to Hai Phong by train
46 What is the thickness of that novel
47 The water was too cold for the children to go swimming
48 Don't forget to wake me up at eight tomorrow morning
49 Were you reading books in the library between 9 and 10 yesterday morning
50 Did you watch television last night

xét ΔABD và ΔEBD, có:

BA = BE (giả thiết)

\(\widehat{ABD}=\widehat{EBD}\) (giả thiết)

BD là cạnh chung

⇒ ΔABD = ΔEBD (c-g-c)

b) sao mà DE = BC được

c) vì BA = BE (giả thiết) nên ΔABE cân tại B

Lại có: BK là đường phân giác  ΔABE

⇒ BK cũng là đường trung trực ΔABE

⇒ KA = KE và \(\widehat{BKE}=\widehat{BKA}=90^0\)

xét ΔDEK VÀ  ΔDAK, có:

KA = KE (cmt)

\(\widehat{DKA}=\widehat{DKE}=90^0\left(cmt\right)\)

DK cạnh chung

=> ΔDEK = ΔDAK (c-g-c)

b) xét ΔANK và ΔBNC, có:

NK = NC (gt)

\(\widehat{ANK}=\widehat{BNC}\) (đối đỉnh)

NB = NA (gt)

⇒ ΔANK = ΔBNC (c-g-c)

vì M là trung điểm của BC nên ta có: \(BC=MB+MC=2MC\)

mà KA = BC (2 cạnh tương ứng)

\(\Rightarrow BC=KA=2MC\)

c) ta có MB = MC (giả thiết) 

⇒ MA là đường trung tuyến của ΔABC

⇒ MA cũng là đường phân giác của ΔABC

⇒ MA là đường phân giác của \(\widehat{BAC}\)

\(\widehat{BAC}=\widehat{BAM}+\widehat{MAC}=2\widehat{BAM}\\ \Rightarrow\widehat{BAM}=\dfrac{\widehat{BAC}}{2}=\dfrac{50^0}{2}=25^0\left(1\right)\)

Vì ΔABC cân tại A nên

\(\widehat{B}=\widehat{C}=\dfrac{\left(180^0-\widehat{A}\right)}{2}=\dfrac{\left(180^0-50^0\right)}{2}=\dfrac{130^0}{2}=65^0\)

mà \(\widehat{KAB}=\widehat{ABC}\) (2 góc tương ứng)

\(\Rightarrow\widehat{KAB}=65^0\left(2\right)\)

Từ (1) và (2) ta có:

\(\widehat{KAM}=\widehat{KAB}+\widehat{AMB}=65^0+25^0=90^0\)

số quyển vở mà cô phát cho cả lớp là:

50 x 60% = 30 (quyển vở)

số quyển vở cô còn lại là:

50 - 30 = 20 (quyển vở)

23858210dm³

1 How about playing badminton this weekend
2 I am more interested in basketball than my brother

\(34\cdot34=34^2=1156\)

\(-207+\left(12-x\right)=11\\ 12-x=11-\left(-207\right)\\ 12-x=218\\ x=12-218\\ x=-206\)