# Cyclic quadrilateral (tangent of the acute angle between the diagonals)

## Description

In Euclidean geometry, a cyclic quadrilateral or inscribed quadrilateral is a quadrilateral whose vertices all lie on a single circle. This circle is called the circumcircle or circumscribed circle, and the vertices are said to be concyclic. The tangent of the acute angle between the diagonals of the quadrilateral can be calculated by the sides and the semiperimeter of the quadrilateral.

Related formulas## Variables

θ | The acute angle between the diagonals (degrees) |

s | Semiperimeter of the cyclic quadrilateral (m) |

b | Length of the side of the cyclic quadrilateral (BC) (m) |

d | Length of the side of the cyclic quadrilateral (DA) (m) |

a | Length of the side of the cyclic quadrilateral (AB) (m) |

c | Length of the side of the cyclic quadrilateral (CD) (m) |