Gọi I là trung điểm của dây cung AB không đi qua tâm của (O; R) . Qua I vẽ dây CD

   a) chứng tỏ CD>=AB. Tìm độ dài nhỏ nhất , lớn nhất của các dây quay quanh I

   b) cho R=5cm; OI=4cm. Tính độ dài dây cung ngắn nhất qua I

   c) chứng tỏ: góc OAI > góc ODI

viết 1 bài văn Chủ Đề : Tình Cảm Gia Đình
Tự sự kết hợp miêu tả và miêu tả nội tâm .

relative clause

chứng minh

(sin x + cos x )² = 1 + 2 . sin x . cos x

sin²a = tg²a / 1+ tg²a 

1.      Yesterday afternoon, my father (fix)…… his bicycle while his mother (côk)….. dinner

2.      I learn to swim when I (be)….. very young. I (teach)…… by my father

3.      My grandfather was a builder. He (build)……  this house many years ago

4.      They (not have )……. a party in the garden at present

5.      I (visit)…… the art museum yesterday, I (never, sê)….. many of Picasso’s paintings before

6.      Dennis (smoke)…… a lot. In fact, whenever I (see)…… him, he (smoke)……

7.      At this time yesterday, I (do)…..  my homework

8.      Don’t make noise . My father  ( listen )….. to the radio

9.      I (finish)….. everything when you come back.

10.  We (live)…. in Da Nang since we (be)….. ten years old.

11.  The students ( play)….. soccer in the yard now.

12.  They ( know)…… each other quite well for ages.

13.  I was having dinner last night when he ( come )…… in.                 

14.  Tom always (drive)…… more carefully at night.

15.  Why didn’t you listen while I (speak)…… to you?

16.  My bicycle isn’t here anymore. Somebody (take)….. it

17.  I hope it (not rain)…… when we start early tomorrow.

18.  My brother (watch)…….TV after he had his dinner.

1.      I (work) on the computer when the earthquake happened

2.      I (have)….. a bath when she phoned

3.      Jame (walk)…….. through the forest when the storm started

4.      I found my pen while I (look )……. for my bag

5.      He (break)…… his arm when he (play)…… tennis

6.      The phone (ring)…… while An (have)……. a bath

7.      At 8 o’clock last night, we (ưatch)…… television

8.      It suddenly (begin)……. to rain while Laura (sit)…… in the garden

9.      When I (see)…… them, they (try)……. to find a new a house near their work

10.  Though she (have)…… her own house, she (stay)….. with her parents now

11.  He (walk)…… along the street when he suddenly (feel)….. something hit him in the back

12.  Last night I (drop)…… a plate when I (do)…… up washing. Fortunately it (not break)…..

13.  That’s the third time he (phone)….. her this evening

14.  Jim (not be )….. here at the moment

15.  Now he (weigh)……. 70 kilograms

16.  (You / have )….. time to write the lesson? – Yes, I did