nick Nguyễn Phúc Nguyên
Cho \(\Delta ABC\) có \(\widehat{A}=120^o\). Các tia phân giác của góc A, C cắt tại O, cắt BC và AB ở D và E. Đường phân giác của góc ngoài tại B của \(\Delta ABC\) cắt AC ở F. CMR:
a) \(BO\perp BF\)
b) \(\widehat{BDF}=\widehat{ADF}\)
c) D, E, F thẳng hàng.
Đưa ra dạng đúng của từ cho trước:
1, I stopped (buy) a newspaper on the way home.
2, Her new novel will (translate) into Vietnamese.
3, He (lose) his job last month and since then he has been out of work.
4, He used to (work) on the farm.
5, They used (go) swimming in the afternoon.
6, I would rather you (do) the test well.
7, It's time we (catch) the bus.
8, A little girl can't (spend) all her time (listen) to stories.
9, You'd better (not smoke) cigarettes.
10, I'm not used to (get) up early. I'd rather (stay) in bed a bit longer.
11, When I (meet) him six years ago, he (work) as a directory for three years already.
12, A woman please. I (not be) ready yet but I (be) in a couple of minute.
13, There is somebody behind us. I think we (follow).
14, You look frozen. Sit down by the fire and I (make) you a cup of coffee.
15, Sally bought a new house last year, but she (not sell) her old one yet.
16, Please be quiet. I (try) to read the paper.
17, I (wait) until he (finish) his next novel.
18, Ann, we (go) to town. (You/come) with us?
19, She (have) coffee for breakfast every morning.
20, She sometimes (buy) vegetable at this market.
21, I (try) to learn English for year, but I (not succeed) yet.
22, That brown suitcase (belong) to Dr. Rice.
23, Up to present, we (write) almost every lesson in the book.
24, We will go when the rain (stop).
25, I (stay) here until he (answer) me.
Bài 1: Cho tam giác ABC có AD, BE, CF cắt tại O. CMR: \(S_{\Delta AOE}=S_{\Delta DEC}=S_{\Delta OCD}=S_{\Delta OBD}=S_{\Delta OBF}=S_{\Delta OFA}=\dfrac{1}{6}S_{\Delta ABC}\)
Bài 2: Cho tam giác ABC có \(AM=\dfrac{1}{2}BC\). CMR: tam giác ABC vuông tại A.