◀ ▲ ▶Branches / Geometry / Elements-euclid / Book--3-circles / Definition: 3.02: Tangent to the Circle, Straight Line Touching The Circle

Definition: 3.02: Tangent to the Circle, Straight Line Touching The Circle

A straight line said to touch a circle is any (straight line) which, meeting the circle and being produced, does not cut the circle.

Modern Formulation

A segment, ray, or straight line is called a tangent to the circle (or is said to touch a circle) when it intersects the circumference of a circle at exactly one point. The point where the tangent to the circle touches the circumference is called the point of intersection.

Mentioned in:

Corollaries: 1 2
Definitions: 3
Proofs: 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Propositions: 23 24 25 26 27 28 29

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References

Adapted from CC BY-SA 3.0 Sources:

1. Callahan, Daniel: "Euclid’s 'Elements' Redux" 2014

Adapted from (subject to copyright, with kind permission)

1. Fitzpatrick, Richard: Euclid's "Elements of Geometry"