Dear Ladies and Gentlemen!
I have discovered two problems with the GeoGebra-command Tangent:
1. By chance I acchieved to construct a tangent from a point which
does NOT lie on the curve, but the parameter-options for the command
Tangent
only contain Tangent[Point on Curve, Curve] (1)
not Tangent[point, curve]! (2)
2. While Tangent works for purpose (2), it does not work for purpose
(1) - for implicit curves at least:
I have considered an implicit curve (algebraic curve, order 3), a
point P in the plane and the tangent from P to c.
A = 1 B = 1 P=(-2,1) c: A x³ + B y = 0
t = Tangent[P,c]
I see 4 tangents to c through P, but if I change P to (0,0), save the
file,reopen it, two windows appear saying: 'opening file failed' and
a new ggb-window is opened but I cannot open the saved file!
Of course it would be easy to solve this problem defining explicitely
f(x) = -x^3 instead of c,
but I am interested in tangents in given points of any algebraic curve
which cannot be defined explicitely!
Best wishes and thanks for clearing this problem!
Walter Lenzenweger
P.S. I am using a Dell-notebook XPS L502X, Windows 7
