# Nagel's Theorem

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Let ABC be a triangle with two altitudes AA' and BB', and let O be the center of the circumcircle. Then A'B' and CO are perpendicular.

Contributed by: Jay Warendorff (March 2011)

After work by: Alexander Bogomolny

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

A. Bogomolny, "Nagel's Theorem," *Interactive Mathematics Miscellany and Puzzles*.

## Permanent Citation