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How to Find Orthocenter and Altitudes with GeoGebra

You can use GeoGebra to find the orthocenter and altitudes of a triangle:

GeoGebra Instruction 1

1.
Open Algebra View and Graphics View under GeoGebra icon View in GeoGebra icon Menu.
2.
Make a triangle with the vertices A, B and C by clicking Polygon GeoGebra icon. Then you need to click on three positions in Graphics View where you want the vertices of the triangle to be. Finally, complete the triangle by clicking on the point that you started with.
3.
Select Perpendicular Line GeoGebra icon. Construct the line from vertex A perpendicular to the opposite side BC, construct the line from vertex B perpendicular to the opposite side AC, and construct the line from vertex C perpendicular to the opposite side AB. These lines are the altitudes.
4.
Select Intersect GeoGebra icon by first clicking tool number 2, then tool number 4 in the drop-down list, and click on two of the altitudes to construct the point of intersection between them. This point is the orthocenter.

Screenshot of GeoGebra showing a triangle with its altitudes and orthocenter

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