From GeoGebra Manual
- Tangents to a conic section can be produced in several ways (see also Tangent command):
- Selecting a point and a conic produces all tangents through the point to the conic.
- Selecting a line and a conic produces all tangents to the conic that are parallel to the selected line.
- Selecting a point and a function produces the tangent line to the function in its point having the same x-coordinate of the selected point (e.g. if the point is A, the tangent is drawn in x = x(A)).
- Selecting two circles produces the common tangents to them (up to 4).
- Note: x(A) represents the x-coordinate of point A. If point A lies on the function graph, the tangent runs through point A.
- Note: Type rather than if you want a conic (parabola) rather than a function.