cho tam giác ABC vuông tại A đường cao AH ( H thuộc BC). biết độ dài AB bằng 5cm, BH=3cm. Tính độ dài các cạnh AC và BC

Cho tam giác ABC vuông tại A.Đường cao AH, kẻ HE ,HF lần lượt vuông góc với AB và AC .Chứng minh:

a) EB/EC=(AB/AC)^3

b) BC.BE.BF=AH^3

Hình thang cân ABCD có đáy lớn CD = 10cm, đáy nhỏ bằng đường cao, đường chéo vuông góc với cạnh bên. Tính đường cao của hình thang cân đó.

the letter has just written by one of my closest friends

sai ở đâu zị, sửa luôn

Cho hình trên ta có tam giác ABC cân tại A, AH đường cao, AH=5 cm, BD=6cm. Tính BC

“We’d better take a taxi to the station.”

“Yes. The train ….. in fifteen minutes.”

A has left B will have left C leaves

“Where is the newspaper?”

“I threw it away. I thought you ….. reading it.”

A have finished B finished C had finished

“I feel very tired.”

“How can you be tired? You ….. a thing all day.”

A haven’t been doing B aren’t doing C haven’t done

“Cathy doesn’t study enough.”

“I know. I’m afraid she ….. her exam.”

A won’t pass B won’t be passing C won’t have passed

“It’s bad news about Janet crashing her new car, isn’t it?

“Yes. She ….. for months to buy it.”

A saved B is saving C had been saving

“There’s someone here to see you.”

“Oh, that ….. my sister. Send her in.”

A will have been B was C will be

“Whose is this earring?”

“I don’t know. I found it when I … the house.”

A was cleaning B had cleaned C am cleaning

“I ….. to reach Jane on the phone all day.”

“Don’t you know? She’s gone on holiday.”

A tried B have been trying C have tried

“I want to visit Katie.”

“Well, don’t visit her before five o’clock. She ….. .”

A is working B will be working C will have worked

“That ….. like Dad’s car.”

“It is. He must have finished work early.”

A sounds B had sounded C has sounded

“Is that a new jumper?”

“No. I ….. it from Laura yesterday.”

A have borrowed B had borrowed C borrowed

“ ….. to the library today?”

“Yes. Would you like me to return your books?”

A Will you have gone B Will you have been going C Will you be going

“How is your grandfather?”

“His condition ….. day by day.”

A improves B has improved C is improving

“When did you speak to Sue?”

“I met her as I ….. to work.”

A had walked B was walking C am walking

“Shall we go shopping?”

“I can’t go until the babysitter ….. .”

A arrives B will arrive C arrived

“I’ve invited Sam to my party.”

“I doubt if he ….. .He’s studying for an exam.”

A comes B will come C is coming

“I’m sorry I’m late.”

“I ….. here for over an hour.”

A have been waiting B have waited C was waiting

“I’m having trouble with the car.”

“I’m sure John ….. you fix it if you ask him.”

A is going to help B helps C will help

“Tina is still looking for a decent flat.”

“How long ….. ?”

A was she looking B is she looking C has she been looking

“Has Paul come to terms with his examination results?”

“Yes. He ….. the fact that he’ll have to resit.”

A had accepted B has accepted C accepted

“Did you have a good time at the Jordans?”

“Not really. I ….. I’ll ever visit them again.”

A don’t think B am not thinking C won’t be thinking

Gerald just can’t ….. working shifts.

A used to B be used C get used to

Alison feels more sympathy and less anger than she ….. .

A had B would C used to

“Will you ….. with the audio-video equipment by 12:30 pm?”

“Possibly, but I’ll let you know beforehand.”

A finish B finished C have finished

“George is in hospital.”

“Yes, I’ve heard he ….. good progress.”

A makes B is making C will make

“I’m getting my work permit next week.”

“It’s about time. You ….. here for two months by then.”

A are B will be C will have been

“How do you like your sushi?”

“Well, it’s really different. It’s the first time I ….. Japanese food.”

A have eaten B eat C am eating

“Wasn’t sacking Mary rather harsh on his part?”

“Not really; he ….. her several times in the past.”

A had warned B was warning C warns

“Where’s Jonathan?”

“He ….. to the travel agent’s.”

A has been B has gone C has been going

“John really ought to lose some weight.”

“You’re right; he ….. very heavily during the walk yesterday.”

A was breathing B had breathing C has been breathing

“I heard Roy and Alice had an argument.”

“Do you know what ….. it this time?”

A has started B started C had been started

“I wonder how Jeff is doing.”

“I haven’t got a clue. It’s been a long time since I ….. to him.”

A have spoken B spoke C had spoken

“It’s a pity she had to pull out of the competition.”

“Yes, especially since she ….. such excellent progress.”

A is making B made C had been making

“Who’s going to collect your mail you’re on holiday?”

“I have ….. asked my cousin.”

A ever B still C already

“Did you get to see Frances in the end?”

“No. She ….. for the airport when I arrived at her home.”

A would leave B was leaving C had left

“Helen moved to London last week.”

“Well, I supposed she’ll find it difficult to ….. on the left.”

A be used to driving B use to drive C get used to driving

“How long have you been with Sears S.A.?”

“By next month I ….. there for a year.”

A will be working B have worked C will have been working

“Did you stay up late yesterday?’

“Not really. I went to bed after Monica ….. .”

A was leaving B had left C leaving

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