What does straight edge mean? This question needs to be answered mathematically. A straight edge means that the line connecting the two ends of a line segment is a straight line. At this time, the ruler can be perpendicular to the ground or inclined to the ground. Taking a vertical line as an example, a vertical line can be defined as a straight line perpendicular to the ground, and its two ends are at two points on the ground.

Straight edges are also widely used in life, such as analyzing and drawing lines according to linear trends. In architectural design, the dimensions of rectangle, triangle and other shapes need to be drawn by straight edges. In addition, in physics, the propagation of light follows the law of straight lines. Using the straight edge law, we can predict the propagation path and behavior of light.

Geometrically speaking, a straight edge refers to the downward trajectory of an object completely supported by equal gravity and pressure. In this case, the object is forced to descend in a straight line, and the straight edge is its trajectory. Therefore, straight edges also have important applications in physics and mechanics.