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“三垂线定理”是《直线和平面》一章中的重点内容。我在讲授这一节时先提出这样一个问题:“屋沿前竖了高8米的旗杆,试用测绳测出杆顶到屋沿墙脚的距离。”稍倾,学生活跃、议论。一学生回答:“爬上旗杆,把测绳一端系在杆顶,另一端拉紧,沿墙脚移动,测绳最短时就表示所求的距离。”“对!求直线外一点到这直线的距离,只要在直线上找到一点,使它与已知点的连线最短。”教者首先肯定了他回答中的正确部分,并给以抽象概
The “three vertical line theorem” is the key point in the “Straight Line and Plane” chapter. When I was teaching this section, I first raised the question of “the flagpole of 8 meters high is erected along the front of the house and the ropes are used to measure the distance from the pole top to the house along the wall.” A student replied: “Climb the flagpole, the rope tied to the top of the rod at one end, the other end taut, along the foot of the wall to move the rope when the shortest means that the required distance.” “Yes! Find a straight line to the straight line Distance, as long as it finds a point on the straight line, minimizing its connection to the known point. ”The teacher first affirmed the correct part of his answer and gave an abstract