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Antecedent of Playfair's axiom: a line and a point not on the line Consequent of Playfair's axiom: a second line, parallel to the first, passing through the point. In geometry, Playfair's axiom is an axiom that can be used instead of the fifth postulate of Euclid (the parallel postulate):
Tangential – intersecting a curve at a point and parallel to the curve at that point. Collinear – in the same line; Parallel – in the same direction. Transverse – intersecting at any angle, i.e. not parallel. Orthogonal (or perpendicular) – at a right angle (at the point of intersection).
Pasch's axiom — Let A, B, C be three points that do not lie on a line and let a be a line in the plane ABC which does not meet any of the points A, B, C.If the line a passes through a point of the segment AB, it also passes through a point of the segment AC, or through a point of segment BC.
The parallel postulate: "That, if a straight line falling on two straight lines make the interior angles on the same side less than two right angles, the two straight lines, if produced indefinitely, meet on that side on which are the angles less than the two right angles."
A line is mapped onto a parallel line. Hence: angles remain unchanged. The ratio of two line segments is preserved. Both properties show: A homothety is a similarity. Derivation of the properties: In order to make calculations easy it is assumed that the center is the origin: .
2) In definition 15 he introduces parallel lines in this way; "Straight lines which have the same direction, but are not parts of the same straight line, are called parallel lines." Wilson (1868 , p. 12) Augustus De Morgan reviewed this text and declared it a failure, primarily on the basis of this definition and the way Wilson used it to prove ...
An auxiliary line (or helping line) is ... a proof of the theorem on the sum of angles of a triangle can be done by adding a straight line parallel to one of the ...
Affine planes satisfy the following axioms (Cameron 1991, chapter 2): (in which two lines are called parallel if they are equal or disjoint): Any two distinct points lie on a unique line. Given a point and line there is a unique line that contains the point and is parallel to the line; There exist three non-collinear points.