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AT
16 tháng 7 2021
b) Từ B kẻ đường vuông góc với BC cắt AC tại E
tam giác BEC vuông tại B có \(AB=AC\Rightarrow A\) là trung điểm CE
Vì tam giác ABC cân tại A có AH là đường cao \(\Rightarrow H\) là trung điểm BC
\(\Rightarrow AH\) là đường trung bình tam giác BEC
\(\Rightarrow AH=\dfrac{1}{2}BE\Rightarrow2AH=BE\Rightarrow4AH^2=BE^2\)
tam giác BEC vuông tại B có BK là đường cao \(\Rightarrow\dfrac{1}{BE^2}+\dfrac{1}{BC^2}=\dfrac{1}{BK^2}\)
\(\Rightarrow\dfrac{1}{4AH^2}+\dfrac{1}{BC^2}=\dfrac{1}{BK^2}\)
CA
1
2 tháng 2 2022
- Xét △OBC có: \(BC\)//\(AD\) (gt).
=>\(\dfrac{OD}{OC}=\dfrac{OA}{OB}\) (định lí Ta-let).
=>\(OD=\dfrac{OA}{OB}.OC=\dfrac{2,5}{2}.3=3,75\) (cm).
18 tháng 3 2023
`861000 cm^3=0,861 m^3`
`6,5 dm^3=6500 cm^3`
`40 m^3= 40000dm^3`
`2/3 dm^3=400 cm^3`
TT
0
Tham khảo bài mình đã từng làm
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 1 to 5.
A stinky gym bug in your kitchen? Who will be more upset by the smell - the men or the women in your family? (1) _______ scientists suggest that women not only smell, but feel, taste, and hear more accurately than men.
Take colors, for example. One study suggests that men are not as good as women at distinguishing between (2) _______ of color, although they focus well on rapidly changing images. As for touch, small fingers have a finer sense of touch, whether male or female.
Hearing is possibly one of the most debated areas, when talking about the senses. Evidence shows that boys hear as well as girls at birth, but with age, a man’s hearing may soon deteriorate. (3) _______, environmental factors could play a role in this. Women may also be better at identifying different flavors (4) _______ need both taste and smell to experience, as studies have shown that they have more taste buds on their tongue.
Going back to the smelly gym bag - yes, it’s likely that Mom will be the most (5) _______ out by it. But is that because women’s brains have more ‘smell cells’ or because you were too lazy to move it?
Question 1:A. Each B. Some C. Another D. Every
Question 2:A. smells B. senses C. shadows D. shades
Question 3:A. Moreover B. Therefore C. However D. Due to
Question 4:A. who B. which C. where D. whom
Question 5:A. taken B. sprung C. mazed D. freaked
Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions.
Question 6: Aren’t you putting the cart before the horse by deciding what to wear for the wedding before you’re invited to it?
A. knowing the horse cart B. do things in the right order
C. doing things in the wrong order D. upsetting the horse cart
Question 7: He is writing a letter of acceptance to the employer with the hope to get his favorite position in the company.
A. confirmation B. refusal C. agree D. admission
Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
Question 8: The letters he would write were full of doom and _______. We still do not know what made
him so depressed.
A. drib B. gloom C. duck D. tuck
Question 9: _______ the person is, the more privilege he enjoys.
A. The rich B. The richest C. As rich as D. The richer
Question 10: My grandparents are quite old now and sometimes they have to _______ up and down steps.
A. be helping B. helped C. help D. be helped
Question 11: Unless we do something now, hundreds of plant and animal species will _______.
A. point out B. die out C. cut up D. make up
Question 12: While she was taking her exams, she _______ a terrible headache.
A. will have B. has C. had D. is having
Question 13: Sceptics claim that looking for alien forms of life in space is like squaring the _______ as they do not exist.
A. ground B. circle C. flag D. school
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