1. If two intersecting straight lines on a plane are parallel to a plane, then the two planes are parallel.
2. If a straight line is perpendicular to two intersecting straight lines on the plane, then the straight line is perpendicular to the plane.
3. If one plane passes through the vertical line of another plane, then the two planes are perpendicular to each other.
4. In space, if two sides of two angles are parallel, then the two angles are equal or complementary.
5. If a straight line is parallel to a plane, the intersection of any plane passing through this straight line and this plane is parallel to this straight line.
6. If two planes are parallel, the intersection line obtained by the intersection of any plane and these two planes is parallel to each other.
7. Two straight lines perpendicular to the same plane are parallel.
8. If two planes are perpendicular, the straight line perpendicular to the intersection line in one plane is perpendicular to the other plane.
9. Three Verticality Theorem: If a straight line in a plane is perpendicular to the projection of a diagonal line in this plane, it is also perpendicular to this diagonal line.
10, inverse theorem of three perpendicular theorems: If a straight line in a plane is perpendicular to a diagonal line of this plane, then the projection of this straight line and this diagonal line is also perpendicular.
The importance of learning mathematics;
1. Mathematics is the foundation of science. Almost all natural sciences, social sciences and humanities need to use mathematics as a basic tool. Therefore, learning mathematics can help us better understand and master the knowledge of other disciplines.
Mathematics is everywhere in our daily life. Mathematics plays an important role from simple arithmetic operation to complex financial investment. Learning mathematics can help us better understand these problems in daily life and solve them.
3. Mathematics is also the key driving force of technological innovation. From computer science to physics, mathematics plays a vital role in promoting scientific and technological progress. Learning mathematics can help us better understand and apply these technologies, and even promote new scientific and technological innovation.