A few notes on space angles

1. The definition of space angle reflects the mathematical idea of planarization of space problems. The angle of space is transformed into an angle formed by intersecting straight lines (such as the angle formed by opposite straight lines, the angle formed by a straight line and a plane) or two rays (such as the plane angle of a dihedral angle).

2. The concept of angle in space is the main point of proof for computational problems in three-dimensional geometry. When the traditional deductive reasoning method to find the above angle, must be written exhaustively made auxiliary straight line, auxiliary plane; must be proved in accordance with the definition of space angle. Then calculate. However, with the analytic and vector methods there is no such requirement.

3. Angles in space include angles formed by intersecting lines and angles formed by parallel lines in plane geometry.