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当平面图形中的某些元素在题意允许范围内作任意变动时,研究图形中相应的某些量是否保持不变,这就是平几中的定值问题。定值问题,对初学者来说是一个难点,这是因为它与通常几何题的不同之处在于(1)在给定条件范围内,有些元素位置可变动;(2)题断中没有明确指出定值的具体数量。怎样克服上述难点,顺利地解决定值问题?一般方法是:(1)审清已知条件中,哪些元素的位置和数量关系具有固定性(如已知两定点,则
When some elements of the plane graph are arbitrarily changed within the allowable scope of the question, it is studied whether the corresponding amount in the graph remains unchanged. This is the fixed value problem in the flat number. The fixed value problem is a difficult point for beginners because it differs from the usual geometric problems in that (1) the position of some elements can be changed within a given condition range; Indicates the specific number of settings. How to overcome the above difficulties and smoothly solve the fixed value problem? The general method is: (1) To clarify the relationship between the position and quantity of the elements in the known conditions (if two fixed points are known,