It is to prove the relationship between lines, lines, surfaces and surfaces.

The first thing to know is that two intersecting lines determine a plane.

Line-plane parallelism means that the straight line out of plane is parallel to the straight line in plane (pay attention to the straight line out of plane)

A vertical line means that a straight line is perpendicular to two intersecting straight lines.

Face-to-face parallelism is a key point

Before the plane is parallel, it must be proved that the straight line and the plane are parallel.

When encountering more complicated solid geometry,

There is no way to build a system and solve it with space vectors.

Most topics don't need to be reduced to absurdity.

When using the reduction to absurdity, it is mostly a problem of ability that the auxiliary line can't do.

Therefore, reduction to absurdity (mostly number theory) will not be used in general exams.

Write when you answer, but don't write when you answer.

According to the definition in the textbook

One step less is a false proposition.

For example, it is essential to infer conclusions according to the conditions of textbooks.