How is the Great Orion Nebula (M42) located precisely relative to the stars in the Belt?

Answer

By extending the line drawn downward (southward) from the Belt through Alnilam by the apparent distance equal to the gap between Alnilam and Mintaka.

The text specifies that extending the line downward from Alnilam by the same apparent distance as the gap separating Alnilam and Mintaka lands almost exactly on the coordinates of the Great Orion Nebula.

How is the Great Orion Nebula (M42) located precisely relative to the stars in the Belt?
astronomystarsskyconstellationOrion