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6 tháng 3 2020

B A K D H E C 1 2

a,Xét tam giác ABD và tam giác EBD

B1^=B2^(gt)

BD(cạnh chung)

BA=BE(gt)

=>tam giác ABD = tam giácEBD (c-g-c)

c,Theo câu a ta có :

BAD^=BED^=90* (góc tương ứng)

=>DE vuông góc với BC

Kết hợp với giả thiết ta có :

DE vuông góc với BC (1)

AH vuông góc với BC (2)

Từ 1 và 2 => DE//AH (từ vuông góc đến song song)

1:

a: \(BC=\sqrt{6^2+8^2}=10cm\)

=>AM=10/2=5cm

b: Xét ΔEBC có

EM vừa là đường cao, vừa là trung tuyến

=>ΔEBC cân tại E

Bài 2:

Xét ΔBAE vuông tại A và ΔBHE vuông tại H co

BE chung

góc ABE=góc HBE

=>ΔBAE=ΔBHE

=>BA=BH và EA=EH

=>BE là trung trực của AH

6 tháng 3 2020

Bạn tham khảo link này :

 https://h.vn/hoi-dap/question/478245.html

Hok tốt 

# Chi

 Read the passage and choose the best answer. When Nick and Jane got their phone bill, they knew something was wrong. They couldn't understand why the new bill was over fifty dollars more than the old one. Then Nick saw the long-distance charges. There were ten calls listed to the town of Rosemont, several hundred miles away."But we don't know anybody in Rosemont," Jane protested. "Where is Rosemont, anyway? Besides, no one would have such a ridiculous phone number as 123-456-7890." Suddenly,...
Đọc tiếp

 Read the passage and choose the best answer.

When Nick and Jane got their phone bill, they knew something was wrong. They couldn't understand why the new bill was over fifty dollars more than the old one. Then Nick saw the long-distance charges. There were ten calls listed to the town of Rosemont, several hundred miles away.

"But we don't know anybody in Rosemont," Jane protested. "Where is Rosemont, anyway? Besides, no one would have such a ridiculous phone number as 123-456-7890." Suddenly, they thought of their twin sons, who were just learning how to count. They must have been playing with pushbuttons on the dial. This turned out to be the right solution to the mystery of their phone bill.

66. Nick and Jane are

A.        friends. B.        twin sons. C. telephonists. D. a married couple.

67. What was wrong with their new phone bill?

A.        It couldn't be understood. B.   It contained ten calls for an unknown town.

C. It was fifty dollars. D. It was several hundred miles away.

68. The word ridiculous in the passage could be best replaced by

A.        funny. B.         unreasonable.C.           foolish. D.       crazy.

69. Which of the following sentences is NOT true?

A.        They Couldn't understood why their phone bill cost much.

B.        There were many long-distance calls in their phone bill.

C.        They had to pay fifty dollars for the bill.

D.        Their twin sons learned how to Count on the dial when they Were out.

70. This in the passage refers to

A.        the phone number 123-456-7890.

B.        Nick and Jane's thought.

C.        the long-distance charge.

D.        their sons' playing with Pushbuttons on the dia1.

 

0
 Read the passage and choose the best answer. Gary Smith yesterday celebrated his twentieth birthday, but he's lucky to be alive. In March this year, he was climbing Ben Nevis, Britain's highest mountain, when he lost his way and spent sixteen hours in sub-zero temperatures."My friends laughed at me for having so much survival equipment, but it saved my life."On the first night, the weather was so bad that it tore his new mountain tent to pieces, so he moved into a Youth Hostel. He left the...
Đọc tiếp

 Read the passage and choose the best answer.

Gary Smith yesterday celebrated his twentieth birthday, but he's lucky to be alive. In March this year, he was climbing Ben Nevis, Britain's highest mountain, when he lost his way and spent sixteen hours in sub-zero temperatures.

"My friends laughed at me for having so much survival equipment, but it saved my life."

On the first night, the weather was so bad that it tore his new mountain tent to pieces, so he moved into a Youth Hostel. He left the hostel at 10.00 the next morning but that afternoon he was in trouble. "I fell off a rock and broke my left leg. I couldn't move."

Mountain rescue team went out to look for Gary, and found him at 9.00 the next morning. A helicopter took him to hospital, where he needed several operations. "Next time, I'll go with my friends, not on my own!" he joked.

1. Howald was Gary when he went climbing?

            A. 16. B.19.   C. 20. D.22.

2. How long did he spend on the mountain?

            A. 10 hours.    B. 16 hours.

            C. 1 night.       D. 2 nights.

3. Which of the following sentences is true?

A.        He didn't take many things with him on his trip.

B.        He spent the first night in his new mountain tent.

C.        He went climbing alone.

D. In spite of his broken leg, his climbing trip was a great success.

4. Which of the following groups of adjectives best describe Gary?

A.        Lost, alone, injured.

B.        Hot, terrible, lucky.

C.        Broken, alive, bad.

D.        Bad, alone, lucky.

5.  All the following sentences sound reasonable EXCEPT

A.        If he hadn't fallen off a rock, he wouldn't have broken his leg.

B.        If the Mountain rescue teams hadn't found him, he would have died.

C.        If he hadn't been operated on, he wouldn't have been able to walk again.

D.        If it hadn't been so cold on the mountain, he wouldn't have lost his way.

 

 

2

1.C

2.B

3.D

4.A

5.C

HOK TỐT!!!!

NHỚ K ĐÚNG CHO MK NHA!!!

6 tháng 3 2020
  1. C
6 tháng 3 2020

A B C M E

a) CMR AC // BE

xét tam giacs AMC và tam giác EMB

có AM = ME (gt)

     BM = MC (M trung điểm BC)

     \(\widehat{AMC}=\widehat{EMB}\left(dd\right)\)

=> tam giác AMC = tam giác EMB (cgc)

=> \(\widehat{MBE}=\widehat{MCB}\)mà chúng ở vị trí so le trong => AC//BE

6 tháng 3 2020

b) bạn tự thêm điểm I và K vào hình vẽ nhé, mình lười :))

ta có I thuộc AC, K thuộc BE nên

IC = AC - AI và BK = BE - KE

mà AC = BE (cmt), AI = KE (gt)

=> IC = BK 

xét tam giác IMC và tam giác KMB

có: BK = IC (cmt)

BM = MC (cmt)

góc MBK = góc ICM (AC//BE)

=> tam giác IMC = tam giác KMB (cgc) 

=> góc IMC = góc KMB

khi đó góc IMK = 180 độ

I, M, K thẳng hàng

25 tháng 3 2020

Câu hỏi của Nguyễn Phúc Minh - Toán lớp 7 - Học toán với OnlineMath

6 tháng 3 2020

B N C A D M

a,Xét tam giác vuông ABD và NBD có 

BD chung

ABD^=NBD^

=>Tam giác ABD = tam giác NBD (ch-gn)

c,Ta có : AB>AD 

NC>ND

Mà AD=ND

=>AB+NC>2AD