Demonstration for constructions of a tangent to a circle,
from a point outside, with a straightedge only
Description of the construction
From the point A, by using the GeoGebra-Dynamic Geometric Software, construct 3 secants of the circle, which intersect it at the points B, C, D, E, F, G . Construct the chords BE, CD, DG, EF. Points H and I denote the points of intersection of the straight lines BE and CD and the straight lines DG and EF, respectively.
Construct a straight line through the points H and I. This line intersects the circle at the points M and N. AM and AN are the tangents to the circle.

Demonstration for constructions of a tangent to a circle,
from a point outside, with a straightedge only
Description of the construction
From the point A, by using the GeoGebra-Dynamic Geometric Software, construct 3 secants of the circle, which intersect it at the points B, C, D, E, F, G . Construct the chords BE, CD, DG, EF. Points H and I denote the points of intersection of the straight lines BE and CD and the straight lines DG and EF, respectively.
Construct a straight line through the points H and I. This line intersects the circle at the points M and N. AM and AN are the tangents to the circle.