Cho tam giác ABC nhọn Các đường cao AM, BN cắt nhau tại K.
a. Chứng minh: Tam giác AKN đồng dạng với tam giác BKM
b. Chứng minh tam giác AKB đồng dạng với tam giác NKM
c. Kẻ MH vuông góc với AC, H thuộc AC. Chứng minh MC2= AC. HC
d. KH giao MN tại I. Kẻ IH vuông góc với AC, E thuộc AC. Gọi F là giao điểm của IE và KM. Chứng minh rằng:\(\frac{1}{KN}+\frac{1}{MH}=\frac{2}{FE}\)
1. She can't go for a walk now because she.......(help) her parents about the house. She often ......... (do) it on mondays
2. Where ......... ( they, spend ) last summer ?
- I .......... ( not, know ), I........... (think ) they ........( be ) in France
3. Wait! Where ...........( you , go )? I.......... (go) to the shop to buy some milk
4. How often ...........( you, swim ) in the lake in summer ? -Two or three times a week
5. Yesterday Tony ..........( do ) exercises, ..........(dress) and .........( have ) breakfast
6. When Sara .......(be) five she ...........(can ) read and write
7. Look! A man .........( swim) in the lake !
8. Don't turn TV on. The boys .........( learn ) the poem by heart
9. Last month she ........( not, work ) in the garden. She .........(be) very ill
10. When..........( usually, he, get up )? He always ............( get up ) at 7 o'clock in the morning but today he ...........( still, sleep ). Yesterday he ...........(paint) the house and ...........( get ) very tired