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许多几何问题虽然与圆无关,但是如果能结合条件补作辅助圆,就能利用圆的有关性质、结论,将某些最值问题通过圆中的几何模型求解.笔者经过研究,归纳为以下情况可考虑作辅助圆:一、同一端点出发的等长线段例1如图1,在直角梯形ABCD中,∠DAB=∠ABC=90°,AD=3,AB=4,BC=6,点E是线段AB上一动点,将△EBC沿CE翻折到△EB’C,连结B’D,B’A.当点E在AB上运
Although many geometric problems have nothing to do with the circle, if the supplementary circle can be made according to the conditions, we can make use of the related nature and conclusion of the circle to solve some of the most value problems through the geometric model in the circle. Can be considered as an auxiliary circle: First, the same end of the starting point of the same length as shown in Figure 1, in the right-angle trapezoidal ABCD, ∠ DAB = ∠ ABC = 90 °, AD = 3, AB = 4, BC = 6, E Is a moving point AB on the line, the △ EBC along the CE folded to △ EB’C, link B’D, B’A.