1,

Áp dụng định lý Py-ta-go vào tam giác AHC vuông tại H ta đc:

\(AH^2+HC^2=AC^2\)

\(\Rightarrow4^2+HC^2=5^2\)

\(\Rightarrow HC^2=9\)

\(\Rightarrow HC=3\left(cm\right)\)

Vì tam giác ABC cân tại A có đường cao AH

=> AH là đường trung tuyến của tam giác ABC

=> H là trưng điểm của BC

=> BC=2HC=2.3=6(cm)

Chu vi tam giác ABC là

AB+BC+AC=5+5+6=16(cm)

2,

Vì tam giác DFE cân tại F có đường cao FM

=> FM là đường trung tuyến của tam giác DFE

=> M là trung điểm của DE

=> \(ME=\frac{1}{2}DE=\frac{1}{2}\cdot8=4\left(cm\right)\)

Áp dụng định lý Py-ta-go vào tam giác FME vuông tại M ta đc

\(FM^2+ME^2=FE^2\)

\(\Rightarrow FM^2+4^2=5^2\)

\(\Rightarrow FM^2=9\)

\(\Rightarrow FM=3\left(cm\right)\)

Diện tích tam giác DFE là:

\(S_{DFE}=\frac{8\cdot3}{2}=12\left(cm^2\right)\)

Bài 1:

Xét \(\Delta AHC\)vuông tại H 

\(\Rightarrow AH^2+HC^2=AC^2\)\(\Rightarrow HC^2=AC^2-AH^2=5^2-4^2=9\)

\(\Rightarrow HC=3\)(cm)

Xét \(\Delta ABC\)cân tại A có AH là đường cao

\(\Rightarrow H\)là trung điểm của BC \(\Rightarrow BC=2HC=2.3=6\)(cm)

\(\Rightarrow\)Chu vi \(\Delta ABC\)\(=AB+AC+BC=5+5+6=16\)(cm)

Vậy chu vi \(\Delta ABC\)là 16cm

Bài 12:

Xét \(\Delta DFE\)cân tại F có FM là đường cao

\(\Rightarrow\)M là trung điểm DE \(\Rightarrow ME=\frac{1}{2}DE=\frac{1}{2}.8=4\)(cm)

Xét \(\Delta EMF\)vuông tại M \(\Rightarrow ME^2+MF^2=EF^2\)

\(\Rightarrow MF^2=EF^2-ME^2=5^2-4^2=9\)

\(\Rightarrow MF=3\)(cm)

\(\Rightarrow S_{FDE}=\frac{1}{2}.MF.DE=\frac{1}{2}.3.8=12\left(cm^2\right)\)

Vậy \(S_{FDE}=12cm^2\)

Tam giác ABC vuông tại A có AM là trung tuyến => AM = MB = MC = BC/2 => tgiac MAC cân tại M => góc MAC = góc MCA Xét tgiac ABC và tgiac CDA có: AC: cạnh chung góc BCA = góc DAC BC = AD ( = 3AM) suy ra: tgiac ABC = tgiac CDA (c.g.c) => góc BAC = góc DCA = 900 hay CD vuông góc với AC

a) Ap dụng định lý Pytago vào tam giác vuông ABC ta có: A B 2 + A C 2 = B C 2 AB2+AC2=BC2 ⇔ ⇔ A C 2 = B C 2 − A B 2 AC2=BC2−AB2 ⇔ ⇔ A C 2 = 10 2 − 8 2 = 36 AC2=102−82=36 ⇔ ⇔ A C = √ 36 = 6 AC=36=6 Vậy....

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Dấu hiệu là đề bài ý

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GócACD=80 độ

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1. Although I didn't find the film at all frightening.

2. Although most cris agreed that the film was her best ever.

3. Despite being a well-reviewed hit.

4. Although Ben Stiller was the star of this movie.

5. Despite those poor reviews.  

6. Despite the fact that they split up over 40 years ago.

7. Although Meryl Streep is more well known for her many Oscar-worthy performances.

8. Despite knowing that it is not true.   

1. Although I didn't find the film at all frightening 

2. Although most cris agreed that the film was her best ever

3. Despite being a well-reviewed hit

4. Although Ben Stiller was the star of this movie

5. Despite those poor reviews

6. Despite the fact that they split up over 40 years ago

7. Although Meryl Streep is more well known for her many Oscar-worthy performances

8. Despite knowing that it is not true

Ex1: Choose the best answer: Question 1: Do you know what is the cause __________ pollution? A. of            B. in       C. on      D. for Question 2: My mother has to measure blood __________ every month A. billboard        B. pressure C. groundwater D. earplug Question 3: __________ pollution is harmful or annoying level of noise, as from vehicles, industry activities, etc. A. light        B. visual C. soil D. noise Question 4: Parents should teach children not to __________ wastes on the road A. litter        B. poison C. cause D. measure Question 5: I can’t hear your voice __________ I’m wearing an earplug A. although        B. due C. however D. because Question 6: His grandfather made him __________ hard when he was small A. study        B. to study C. studying D. studied Question 7: This picture __________ the contamination of ground water. A. illustrate        B. illustrating C. illustrates D. illustrated Question 8: Could you list some non-point source __________? A. pollution        B. pollutants C. polluting D. polluted Question 9: Scientists has just come up __________ a solution to hearing loss A. to            B. on C. with D. down Question 10: If we dump a plastic into the ground, it __________ a long time to disappear. A. will take        B. take C. took D. takes Question 11: Pollutions are harmful __________ human health A. with        B. at C. to D. on Question 12: __________ water resulted in the death of many aquatic animals. A. Contaminate    B. Contaminated C. Contaminating D. Contamination Question 13: What would you do if a factory in your neighborhood __________ untreated water into the river? A. dump        B. dumped C. dumping D. dumps Question 14: Have you ever heard about the __________ of radioactive pollution? A. affects        B. effects C. pollutes D. poisons Question 15: : __________ pollution is the increase of temperature caused by human activity. A. visual        B. water C. thermal D. radioactive Ex2: Supply the correct form of the verbs in brackets 1. Lan often (do) __________ her homework. 2. They (play) __________ tennis now. 3. Lan (buy) _________ a car since 2000. 4. Minh (watch) _______ TV last night. 5. Hoa (meet) _________ Lan tomorrow. 6. Football (play) ________ by boys. Ex3: Find and correct mistakes: 1.What about watch TV?  A. What        B. about        C. watch 2.Do you mind if I listened to music?  A. mind        B. listened        C. to 3.What do you do yesterday? A. What        B. do            C. yesterday 4.My dog is different with her dog. A. is            B. with        C. her Ex4: Rewrite sentences without changing the meaning. 1. Let’s go to the zoo! What about .......................................................................? 2. Ba enjoys skipping. Ba likes .............................................................................. 3. Long should work harder. Long ought to .................................................................... 4. Would you mind opening the door? Do you mind ......................................................................? 4. I can’t tell you unless you tell me what’s wrong. (if) -> ………………………………………………………… 5. Nhung didn’t go to the cinema with her friends because her younger sister was ill. -> Because of ……  6. Eating too much sugar can result in health problem. (lead to) -> ………………………………………………………………… 7. Minh isn’t hard working, so he often gets bad marks. (if) -> ………………………………………………………… 8. I’m not you. But I think you should recycle these plastic carrier bags. (If) -> ………………………………………………………… Ex5: Use the correct form of the words given to complete the sentences. 1. This volcano is dead; it has been (ACT) _____ for more than a century. 2. The Earth would be a happy planet if human beings, animals and plants (PEACE) _____ co-existed. 3. The chemical (POLLUTE) _____from cars and factories make the air, water and soil dangerously dirty. 4. You cannot imagine how (SERIOUS) _____the area was damaged by the flood. 5.  Scotland is a ……….. land and this is noted for its rich and interesting history. (legend)

1

a. y=48/x

b. y=16/3

c. x=-12

2

a. x=-60/y

b. y=-10, 5

c. x= 30, -2

1 A,y=48/x B,y=16/3 C,x=-12 2 A,x=-60/y B,y=-10,5 C,x=30,-2 A,

C, C, B, C, A, C

 từ 1=> 6 đó

1,C .2,C.3,B.4,B.5,D.6,D.