题目

如图，四边形内接于，是的直径，与交于点E，切于点B．（1）求证：；（2）若，，求证：． 答案：【答案】（1）见详解；（2）见详解【解析】（1）由圆周角定理的推论，可知∠ABC=90°，由切线的性质可知∠OBP=90°，进而即可得到结论；（2）先推出，从而得∠AOB=40°，继而得∠OAB=70°，再推出∠CDE=70°，进而即可得到结论．证明：（1）∵是的直径，∴∠ABC=90°，∵切于点B，∴∠OBP=90°，∴，∴；（2）阅读理解 　　Scientists say Severe Acute Respiratory Syndrome (SARS) is caused by a new virus from the family of corona viruses (冠状病毒), which also causes the common cold. 　　WHAT ARE THE SYMPTOMS? 　　The World Health Organization says the main symptoms of SARS are high fever (over 38℃), dry cough, shortness breath or breathing difficulties. Changes in chest X-rays, which are indicative of pneumonia (肺炎), also occur. SARS may be associated with other symptoms, including chills, headache, muscular stiffness, loss of appetite, malaise, confusion, rash and diarrhea. 　　Health experts say the disease has an incubation period (潜伏期) of between two-to-seven days, with three-to-five days being more common, before victims start showing flu-like symptoms. 　　HOW DANGEROUS IS IT? 　　The mortality rate (死亡率) appears to be between 3 to 5 per cent. In Hong Kong, at least, those who infected invariably develop severe pneumonia, which can cause numerous complications. The victim's condition can deteriorate (恶化) very quickly in as little as five days. 　　WHAT IS THE TREATMENT? 　　There is currently no specific cure for the disease. But doctors worldwide have been treating it with ribavirinan anti-viral drugand steroids (类固醇). Doctors say if treated early mast patients without other serious illnesses can recover. 　　HOW DOES IT SPREAD? 　　WHO (世界卫生组织) and Hong Kong experts say the virus spreads through droplets by sneezing or coughing and such direct infection (传染) can usually happen within a radius of around three feet. 　　The virus can also spread indirectly as it can survive outside of the human body for three to six hours. Contact with any object that is tainted by droplets containing the virus, for example, a contaminated phone, could lead to infection if a person then touches their eyes, nose or mouth. 　　Health experts have not ruled out that it could be airborne (空气传播的), which infinitely raises the contagious nature of the virus and would make it far harder to contain (控制). 1．Which of the following is NOT considered as one of the symptoms of SARS? [　　] A．dry coughB．shortness of breath C．bleedingD．loss of appetite 2．It is possible that a person will be infected with SARS if ________. [　　] A．they touches their nose after contacting with a contaminated phone. B．they don't wash their hands twice a day. C．they don't know the contagious nature of the virus like health experts. D．they don't go to a doctor at once when they catch a cold. 3．Which of the following is NOT true according to the passage? [　　] A．Even though there is currently no specific cure, the doctors can treat SARS with an anti-viral drug. B．Before victims show flu-like symptoms, SARS has an incubation period of between two-to-seven days. C．That SARS could be airborne has not been ruled out by health experts from WHO. D．Doctors believe that every victim without other serious illnesses can be cured. 4．From the information given in the passage we can deduce that ________. [　　] A．SARS is a type of pneumonia which is caused by influenza. B．When an infected person travels, he can not spread the virus to other passengers on his flight. C．In order to control the spread of the disease, patients should be placed in an isolation unit. D．Wearing a mask is not a good way of keeping off SARS.