# Compass Equivalence Theorem

The compass equivalence theorem is an important statement in compass and straightedge constructions. In these constructions it is assumed that whenever a compass is lifted from a page, it collapses, so that it may not be directly used to transfer distances. While this might seem a difficult obstacle to surmount, the compass equivalence theorem states that any construction via a "fixed" compass may be attained with a collapsing compass. In other words, it is possible to construct a circle of equal radius, centered at any given point on the plane. This theorem is known as Proposition II of Book I of Euclid's Elements.

### Other articles related to "compass equivalence theorem, compass equivalence, compass, theorem":

Compass Equivalence Theorem - Alternative Construction Without Straightedge
... It is possible to prove compass equivalence without the use of the straightedge ... This justifies the use of "fixed compass" moves in proofs of the Mohr-Mascheroni theorem, which states that any construction possible with straightedge and compass can be accomplished ... wish to construct a circle centered at A with the same radius as BC, using only a collapsing compass and no straightedge ...

### Famous quotes containing the words theorem and/or compass:

To insure the adoration of a theorem for any length of time, faith is not enough, a police force is needed as well.
Albert Camus (1913–1960)

It is the star to every wand’ring bark,
Whose worth’s unknown, although his height be taken.
Love’s not Time’s fool, though rosy lips and cheeks
Within his bending sickle’s compass come;
Love alters not with his brief hours and weeks,
But bears it out even to the edge of doom.
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