请给我详细讲解---同步课堂 **人口统计图的判读** **2. 平面正三角形坐标图的判读** 如图判断“•”各年龄段的人口比重,可以采用平行线法, 该法分三步: (1) 沿着三个坐标轴数值增大的方向画出三个箭头,如图中的箭头①②③。 (2) 过图中标出的点“•”,分别画出与上述三个箭头平行且延伸方向一致的三条斜线。 (3) 读出上述斜线与三个坐标轴的交点坐标,这就是待求点在三个坐标轴上的坐标。在图中待求点“•”的三个坐标是0~14岁为23%, 15~64岁为73%, 65岁及以上为4%。 注意 皆为百分比,不是实际人口数量,各构成要素所占比重的总和必然是100%) **Chart Description:** * **Type:** Planar equilateral triangle coordinate chart (Ternary plot) * **Main Elements:** * Equilateral triangle shape. * Three axes representing proportions of different age groups. * **Bottom Axis:** Labeled "0-14岁" (0-14 years old). Scale runs from 0% on the left to 100% on the right. Arrow ① points to the right, indicating the direction of increasing value for this axis. * **Right Axis:** Labeled "15-64岁" (15-64 years old). Scale runs from 0% at the top vertex to 100% at the bottom right vertex, increasing downwards along the right side. Arrow ② points downwards along the right side, indicating the direction of increasing value. * **Left Axis:** Labeled "65岁及以上" (65 years and above). Scale runs from 0% at the bottom left vertex to 100% at the top vertex, increasing upwards along the left side. Arrow ③ points upwards along the left side, indicating the direction of increasing value. * Grid lines are drawn parallel to the sides at 20% intervals. * A point labeled "•" is plotted inside the triangle. * Three dashed lines originate from the point "•", each parallel to one of the arrows ①, ②, or ③, extending towards the opposite side/axis. These dashed lines intersect the axes, indicating how to read the coordinates of point "•". * Based on the dashed lines and the scales, the point "•" corresponds to approximately 23% on the 0-14 axis, 73% on the 15-64 axis, and 4% on the 65+ axis, as stated in the text. 第三节 人口容量