Here is a construction of the Euler Line. The interactive features show that even when the triangle is moved and manipulated, the Euler Line still passes through the centroid, circumcenter, and orthocenter.
Interactive Graphing Circles Ex 1A
Shadows and Eclipses
NS1-02-P4a2-CYU3-RQ3 (Product Rule)
Solving Calculus Problems with Geogebra
Shadows in Perspective
Solving Calculus Problems with Geogebra 3