A cyclic pentagon is a not necessarily regular Pentagon on whose Vertices a Circle may be
Circumscribed. Let

(1) |

(2) | |||

(3) | |||

(4) | |||

(5) | |||

(6) |

Then define

(7) | |||

(8) | |||

(9) | |||

(10) | |||

(11) |

The Area of the pentagon then satisfies

(12) |

(13) |

**References**

Robbins, D. P. ``Areas of Polygons Inscribed in a Circle.'' *Discr. Comput. Geom.* **12**, 223-236, 1994.

Robbins, D. P. ``Areas of Polygons Inscribed in a Circle.'' *Amer. Math. Monthly* **102**, 523-530, 1995.

© 1996-9

1999-05-25