Texas Instruments
Texas Instruments: Does Your Euler Line "Wiggle"?
The students will construct an Euler line and demonstrate it is an Euler line by "wiggling" the triangle to guarantee the correct centers remain on the line.
Math Open Reference
Math Open Reference: Centroid of a Triangle
A complete reference guide to the centroid of a triangle. It provides definitions, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
Math Open Reference
Math Open Reference: Orthocenter of a Triangle
Learn about the orthocenter of a triangle with this handy reference guide. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
Cut the Knot
Cut the Knot: Existence of the Orthocenter
This site defines the altitude of a triangle and gives the standard notation for altitudes of a triangle. The site then goes to list several proofs involving altitudes and orthocenters.
Math Open Reference
Math Open Reference: The Circumcenter of a Triangle
Learn about the circumcenter of a triangle with this handy reference guide. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.