- For any two distinct points $A,B,$ there is exactly one straight line $l$ such that $A,B$ lie on $l.$ We write $AB=BA=l.$
- Any two points $A,B$ which lie on a straight line $l,$ completely determine that straight line, i.e. if $AB=l$ and $AC=l$ and $B\neq C$ then $BC=l.$
- There are at least two distinct points that lie on a given straight line. There are at least three distinct points that do not lie on the same straight line.

- For any three distinct points $A, B, C$ which do not lie on the same straight line, there is exactly one plane $\alpha$ such that $A, B, C$ lie on $\alpha.$ We write $ABC=\alpha.$
- Any three distinct points $A, B, C$ which lie on a plane $\alpha$ but do not lie on the same straight line completely determine that plane.
- If two distinct points $A, B$ lie both on a line $l$ and a plane $\alpha,$ then all points which lie on $l$ also lie on $\alpha.$ We also say that $l$
**is on the plane**$\alpha.$ - If a point $A$ lies on two distinct planes $\alpha,\beta$ then there is at least another point $B$ which also lies on them.
- There are at least four distinct points which do not lie on the same plane.

| | | | | created: 2019-12-21 06:36:30 | modified: 2019-12-21 18:44:16 | by: *bookofproofs* | references: [6260], [8231], [8251], [8324]

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[8231] **Berchtold, Florian**: “Geometrie”, Springer Spektrum, 2017

[8324] **Hilbert, David**: “Grundlagen der Geometrie”, Leipzig, B.G. Teubner, 1903

[8251] **Klotzek, B.**: “Geometrie”, Studienbücherei, 1971

[6260] **Lee, John M.**: “Axiomatic Geometry”, AMC, 2013