Interoperable interactive geometry for Europe
I forgot my login data

Report a bug

Fan club

Quick Intro Videos
click to start movie
Create A Simple
GeoGebra Resource (25Mb)
click to start movie
Filing a review
click to start movie
Find a Resource

This platform is brought to you by the intergeo project, funded under the eContent Plus programme of the European commission and by partners


circle_tangent_lines_by_point ( new line t1, new line t2, circle c, point P)

Given a circle and a point, this constraint returns the two tangents to the circle that pass through that point. The circle can actually be any type within the circle_family.

If there is only tangent because the point is on the circle, each DGS is free to return the tangent twice or return the tangent and an undefined value. If there is only one tangent because the circle is actually an arc which is missing the second tangency point, then the first line should be the unique tangent and the second line should be the undefined value.

If there are no tangents (point inside circle), each DGS is free to return two complex lines or two undefined values.


  1. tangents to circle example: source JSXGraph