There are three criteria for the parallelism of two straight lines:
(1) Two straight lines are cut by the third straight line. If congruent angles are equal, two straight lines are parallel. Abbreviation: same angle, two straight lines are parallel.
(2) Two straight lines are cut by a third straight line. If the internal dislocation angles are equal, two straight lines are parallel. Abbreviation: internal dislocation angles are equal and two straight lines are parallel.
(3) Two straight lines are cut by a third straight line. If they are complementary to each other, the two straight lines are parallel. Abbreviation: the internal angles on the same side are complementary and the two straight lines are parallel.
Extended data
Using linear function to solve practical problems
General steps of establishing mathematical model and solving practical problems by using linear function
(1) Through experiments, a sufficient number of corresponding values of two variables are obtained through measurement.
(2) Establish an appropriate rectangular coordinate system. In the coordinate system, take the corresponding value as the coordinate point and draw the function image.
(3) Observe the image features and determine the function type.
(4) Using the obtained empirical formula, the required results are further obtained.