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Pitot Theorem

Geometry

The Pitot Theorem states that a convex quadrilateral has an inscribed circle tangent to all four sides if and only if the sums of the lengths of its two pairs of opposite sides are equal. Named for Henri Pitot, it is a classical characterization of tangential quadrilaterals, the quadrilateral counterpart to the simpler fact that every triangle always has an inscribed circle.

Facts
Statement
In a tangential quadrilateral the two pairs of opposite sides have the same total length. 1
Proof Year
1725 1
Classification
Statement Form
Identity or Equation 1
Connections

Has Statement Form

Equation, Concepts
Identity, Concepts

In Branch

Source Pitot theorem (Wikipedia)

Proved By

Source Pitot theorem (Wikipedia)
Sources
1. Pitot theorem (Wikipedia)
  • Statement and converse, first sentence
    in a tangential quadrilateral the two pairs of opposite sides have the same total length.
  • History: Henri Pitot proved his theorem in 1725
  • In Branch: Geometry, Lead sentence
    The Pitot theorem in geometry states that in a tangential quadrilateral the two pairs of opposite sides have the same total length
  • Proved By: Jakob Steiner, Lead
    Henri Pitot proved his theorem in 1725, whereas the converse was proved by the Swiss mathematician Jakob Steiner in 1846.
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