# Brianchon's Theorem

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## Contents

## Theorem

Let tangents to $6$ points on a conic section $K$ form a hexagon $H$ to circumscribe the $K$.

Then the main diagonals of $H$ meet at a single point.

## Proof

## Also see

## Source of Name

This entry was named for Charles Julien Brianchon.

## Sources

- 1986: David Wells:
*Curious and Interesting Numbers*... (previous) ... (next): $6$ - 1997: David Wells:
*Curious and Interesting Numbers*(2nd ed.) ... (previous) ... (next): $6$ - 2008: David Nelson:
*The Penguin Dictionary of Mathematics*(4th ed.) ... (previous) ... (next): Entry:**Brianchon's theorem**