Constructing a Parallel Line through an Inaccessible Point

Given a straight line and two lines and that intersect at an inaccessible point , construct a straight line through parallel to . You can drag or .
The general method for solving this problem is to use a transformation so that the inaccessible point becomes the accessible point . In this case, the transformation is a translation in the direction of .
Using the slider, translate and parallel to to and such that the corresponding translates of and intersect at the accessible point .
Then draw the line through parallel to .


  • [Snapshot]
  • [Snapshot]
  • [Snapshot]


[1] B. I. Argunov and M. B. Balk, Elementary Geometry (in Russian), Moscow: Prosveščenie, 1966 pp. 338–339.
    • Share:

Embed Interactive Demonstration New!

Just copy and paste this snippet of JavaScript code into your website or blog to put the live Demonstration on your site. More details »

Files require Wolfram CDF Player or Mathematica.