When two straight lines intersect:

1, find the intersection of two straight lines. Use the intersection point to set the required linear equation (just set an unknown k).

2. Find a specific point on a symmetrical straight line (easy to calculate), use this point to find out that the distance between the known straight line and the required straight line is equal, and list the relationship to solve the slope k,

Expand knowledge:

A straight line is the trajectory of a point in a plane or space moving in a certain direction and its opposite direction; A line that does not bend. Straight line is the basic concept of geometry, which has different descriptions in different geometric systems. Here we mainly describe the straight line in Euclidean space. For other straight lines with non-zero curvature, please refer to non-Euclidean geometry.

Euclidean geometry studies the situation in zero curvature space. It does not define points, lines, surfaces and spaces, but describes the relationships among points, lines and surfaces through axioms. A straight line in Euclidean geometry can be regarded as a set of points, and any point in this set is on a straight line determined by any other two points in this set.

"There is only one straight line when crossing two points" is an axiom in Euclid's geometric system. "There is only one straight line" means "determination", that is, two points determine a straight line.

In geometry, a straight line has no thickness, no end, no directionality, infinite length and definite position.

1, the definition of a straight line is that there are no endpoints at both ends, which can extend to both ends indefinitely and the length cannot be measured.

2. A straight line is the basic concept of geometry, which is the trajectory of a point in space moving in the same or opposite direction. Or defined as: curve with minimum curvature (arc with infinite radius).

There is only one straight line between two points on the plane, that is, two points determine a straight line. On the sphere, countless straight lines can be made after two points.

Since Euclid's Elements of Geometry came out two thousand years ago, classical geometry has been a model of mathematical axiom system for a long time.

Although the position of classical geometry in modern mathematics has declined, its concise theoretical basis, beautiful conclusions and basic proof logic are worth studying.

At the same time, the combination of numbers and shapes is also an important idea in mathematics, and geometry expresses abstract mathematics in another concrete form.

On the other hand, the author thinks that the position of classical geometry in the existing junior high school mathematics is too high, accounting for nearly half of the proportion, while classical geometry has little effect after entering senior high school, so the geometric part will be carried out in parallel with classical geometry and analytical geometry.