在绘制正五棱柱(锥或台)的直观图时,常遇到画正五边形的问题.画正五边形的方法很多,有近似作图法,也有精确作图法(不含视力误差).已知正五边形的一边长a(这是画正五棱柱等常给的条件)作正五边形,我常用如下方法: 1)作线段AB,使AB=a; 2)作线段AB的中垂线HF,H为垂足; 3)以H为圆心,a为半径画弧交HF于Q,连结AQ并延长,以Q为圆心,1/2 a为半径画弧交AQ的 When drawing a direct pentagonal prism (cone or table), it often encounters the problem of drawing a regular pentagon. There are many ways to draw a regular pentagon. There are approximation mapping methods and accurate mapping methods (without eyesight) Error). Known regular pentagons on one side of the length a (this is a regular pentagonal prism and other commonly given conditions) as a regular pentagon, I used the following methods: 1) for the line AB, so that AB = a; 2) for The vertical line HF, H of the line segment AB is the pedestal; 3) The center of the circle is H, and the arc is a circle. HF crosses HF to Q, connects AQ and extends, Q is the center, and 1/2 a is the radius. of