Axiom 2: When three points that are not on a straight line intersect, there is one and only one plane.
According to axiom 2, there are three inferences:
1. A straight line and a point outside the straight line define a plane.
2. Two intersecting straight lines define a plane.
3. Two parallel straight lines define a plane.
Axiom 3: If two non-coincident planes have a common point, then they have one and only one common straight line passing through the point.
Axiom 4: Two lines parallel to the same line are parallel to each other.
Theorem: If two sides of two angles in space are parallel to each other, then the two angles are equal or complementary.
Theorem: A straight line out of the plane is parallel to a straight line in this plane, so this straight line is parallel to this plane.
Theorem: Two intersecting straight lines in a plane are parallel to another plane, then the two planes are parallel.
Theorem: A straight line is parallel to a plane, so the intersection of any plane passing through this straight line and this plane is parallel to this straight line.
Theorem: A graph passes through two parallel planes and intersects the third plane at the same time, so their intersection lines are parallel.
Theorem: If a straight line is perpendicular to two intersecting straight lines on a plane, it is perpendicular to the plane.
Theorem: If one plane intersects the perpendicular of another plane, then the two planes are perpendicular.
Theorem: Two straight lines perpendicular to the same plane are parallel.
Theorem: If two planes are perpendicular, the straight line perpendicular to the intersection of one plane is perpendicular to the other plane.
I think when studying this chapter, you should first listen to the class well, and then do some exercises. It is best to design some axioms and theorems for each question, so that you can use them flexibly. It's best to draw inferences from others.
To do this kind of problems, we should use these theorems and axioms flexibly, at the same time, we should be able to draw pictures and have imagination, and think of straight lines and planes as wireless extensions.
In the exam, the combination of numbers and shapes is the most important, because it can help you solve problems faster.
Also pay attention to the square number, root number and absolute number in the formula.
Well, that's it.