Proposition: Prop. 11.26: Construction of Solid Angle equal to Given Solid Angle

Euclid's Formulation

To construct a solid angle equal to a given solid angle on a given straight line, and at a given point on it. * Let $AB$ be the given straight line, and $A$ the given point on it, and $D$ the given solid angle, contained by the rectilinear angles $EDC$, $EDF$, and $FDC$. * So, it is necessary to construct a solid angle equal to the solid angle $D$ on the straight line $AB$, and at the point $A$ on it.


Modern Formulation

(not yet contributed)

Proofs: 1

Proofs: 1

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Adapted from (subject to copyright, with kind permission)

  1. Fitzpatrick, Richard: Euclid's "Elements of Geometry"

Adapted from CC BY-SA 3.0 Sources:

  1. Prime.mover and others: "Pr∞fWiki",, 2016