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在绘制抛物线的图形时,往在花了一定的精力,也难以准确地绘制出这种曲线来。一般只能采用近似画法,如图1所示:由抛物线定义,先作好直角坐标xy和原点o,再画出标线l、垂足k和焦点F,并在x轴上任取一系列的点A_1 、A_2、A_3,……,过其各点作y轴的平行线,再分别以KA_1,KA_2,KA_3……为半径,F为圆心作弧,交各垂线于P_1和P_1′,P_2和P_2′,P_3和P_3′,……,然后用光滑的曲线顺势连接各点就得到了所求的一条近似的抛物线。由于是近似画法,当然不可能很正确,而且工作量大。为解决上述问题,我们制作一种比较简单而又实用的绘图仪器——抛物线规,可供有关绘图人员使用。本文作简单介绍,愿和绘图仪器研制单位共同商讨,使其逐步完善。
When drawing a parabolic graphic, it takes a certain amount of energy and can not accurately draw such a curve. Generally can only approximate drawing, as shown in Figure 1: defined by a parabola, first rectangular coordinates xy and origin o, and then draw the marking l, foot k and focus F, and take a series of x-axis The points A_1, A_2, A_3, ..., through their respective points as the parallel lines of the y axis, and then take KA_1, KA_2, KA_3 ... as the radius, F as the center of the arc, , P_2 and P_2 ’, P_3 and P_3’, ..., and then smooth the curve with the homeopathic connection to get the point of an approximate parabola. Of course, it can not be correct because of approximate painting, and the workload is heavy. In order to solve the above problems, we make a relatively simple and practical drawing instrument - a parabolic gauge, which can be used by the draftsman concerned. This article is a brief introduction, is willing to discuss with the drawing instrument development unit, making it gradually improved.