The analysis process is as follows:
One of the four angles formed by the intersection of two straight lines is a right angle, that is, the two straight lines are perpendicular to each other, one of which is called the perpendicular of the other straight line, and the intersection point is called the vertical foot.
There are countless points on a straight line, one of which can be used as a vertical line, so a straight line has countless vertical lines, as shown in the following figure:
Extended data:
A straight line is a part of a surface and then constitutes a body. There is no end point, extending to both ends indefinitely, and the length cannot be measured. A straight line is an axisymmetric figure.
It has countless axes of symmetry, one of which is itself, and all lines perpendicular to it (there are countless axes of symmetry). There is only one straight line between two non-overlapping points on the plane, that is, two non-overlapping points determine a straight line. On the sphere, countless similar straight lines can be made after two points.
The basic properties of the vertical line are:
(1) crosses a point on or outside a straight line, and one and only one straight line is perpendicular to the known straight line.
(2) The vertical line segment is the shortest line segment connecting from a point outside the line to all points on the line.