# Inscriptible Quadrilateral: An Illustration

The applet below illustrates the theorem of Pitot.

For a quadrilateral ABCD circumscribed around a circle the sums of opposite sides are equal:

AB + CD = BC + DA.

What if applet does not run? |

The commonly given proof of the converse contains a subtle flaw which is not at all simple to fix. But an additional proof smoothes the wrinkles.

### Inscriptible (tangential, circumscribed) Quadrilateral

- When A Quadrilateral Is Inscriptible?
- Inscriptible Quadrilateral: An Illustration
- Inscriptible and Exscriptible Quadrilaterals
- Pairs of Incircles in a Quadrilateral
- Butterfly in Inscriptible Quadrilateral
- Inscriptible Quadrilateral of Triangle Incenters
- Perpendicular Bisectors in an Inscriptible Quadrilateral II
- A Property of Inscriptible Quadrilaterals
- An Inradii Relation in Inscriptible Quadrilateral

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