Proposition: 3.17: Construction of Tangent from Point to Circle

(Proposition 17 from Book 3 of Euclid's “Elements”)

To draw a straight line touching a given circle from a given point. * Let $A$ be the given point, and $BCD$ the given circle. * So it is required to draw a straight line touching circle $BCD$ from point $A$.


Modern Formulation

It is possible to construct a tangent to a given circle.

Proofs: 1

Proofs: 1
Sections: 2

Thank you to the contributors under CC BY-SA 4.0!



Adapted from (subject to copyright, with kind permission)

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

Adapted from CC BY-SA 3.0 Sources:

  1. Prime.mover and others: "Pr∞fWiki",, 2016