Cho đường tròn tâm O đường kính AB. Dây CD vuông góc với AB tại E (E nằm giữa A và O; E không trùng A, không trùng O). Lấy điểm M thuộc cung nhỏ BC sao cho cung MB nhỏ hơn cung MC. Dây AM cắt CD tại F. Tia BM cắt đường thẳng CD tại K. 1.Chứng minh tứ giác BMFE nội tiếp. 2.Chứng minh BF vuông góc với AK và EK.EF = EA.EB 3.Tiếp tuyến của (O) tại M cắt tia KD tại I. Chứng minh IK = IF.

                                   STRESS AND ATHLETIC SUCCESS                                     

Success, in any field, is often a matter of how well a person is (56) ………… to control the amount of stress they experience. As stress increases, their performance often improves, but (57) …………. is a certain point beyond which their performance begins to decline sharply. Sports psychologists now help Olympic athletes, among others, balance the good and (58) ………… effects of stress.

Before an athletic event, a high level of excitement can actually have a positive effect on the athlete. This excitement becomes harmful, (59) …………., if negative thoughts take over. Thoughts such as “What if I fail?” or “I know the others are better than me” should definitely (60)…………. avoided. Psychologists help athletes manage to replace negative thoughts with positive (61) ………… .

Another useful technique before competing (62) …………to recognize your level of excitement and adjust it if necessary. Music may be helpful in these cases. If you’re over-excited, listening to soft music can help to calm you (63) …………. . If you feel you’re not excited enough, you may want to listen to fast, powerful music to (64) ….…….. your spirits.

The key to success, in other words, is a person’s knowledge of their ideal level of excitement. An imbalance either way could mean the difference (65) ….…….. success and failure.

Help me!!!!!!!!!!!

Cho a+b=2.Chứng minh: a²+b² ≥ 2