See section 12.7.7 for tangents in the plane.
The tangent command takes as argument a geometric object and a point on the object.
tangent draws and returns the plane through the point tangent to the object.
Input:
then:
Output:
If the geometric object is the graph of a function, then the second
argument is a point in the domain of the function; the corresponding point
on the graph will be used.
Input:
then:
Output: