Euclid Book 4

Proposition 5

Construction

Statement

Statement HTML

To circumscribe a circle about a given triangle.

Construction steps

Construction Steps HTML

  • Let △ABC be the given triangle.
  • Construct the perpendicular bisector of CA and the perpendicular bisector of CB. Let O be the intersection of these two lines.
  • Construct the circle through the point A centered at O. This circle has been circumscribed about the given △ABC.
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    Original statement

    πϵρὶ τὸ δοθὲν τρίγωνον κύκλον πϵριγράψαι.

    English translation

    About a given triangle to circumscribe a circle.

    Computable version

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