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影子是一种常见的自然现象.当光线碰到不透明的物体时,就会产生影子.无论是在阳光下,还是在灯光下,影子与我们总是“形影不离”.因为光在同一均匀介质中沿直线传播,因此,只要构建出光线、实物与影子所组成的几何图形,形影结合就可以轻松地解决许多问题.例1高为12.6米的教学楼ED前有一棵大树AB(如图1).某一时刻测得大树AB、教学楼ED在阳光下的投影长分别是BC=2.4米,DF=7.2米,求大树AB的高度.
The shadow is a common natural phenomenon, when the light hits the opaque object, it will produce the shadow.Whether in the sun, or in the light, the shadow and we are always “inseparable” because the light in the same uniform Media, along a straight line, so as long as the construction of light, physical and shadow composed of geometric shapes, shadow combination can easily solve many problems.Example 1 12.6 meters high school building ED before a big tree AB (such as Figure 1) Measured at a time tree AB, ED school building in the sun projection length is BC = 2.4 meters, DF = 7.2 meters, find the height of the tree AB.