MyWikiBiz, Author Your Legacy — Friday March 14, 2025
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<pre>
<pre>
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The "indicator function" or the "characteristic function" of a set Q c X,
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written "f_Q", is the map from X to the boolean domain %B% = {%0%, %1%}
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that is defined in the following ways:
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1. Considered in its extensional form, f_Q is the subset of X x %B%
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that is given by the following formula:
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f_Q = {<x, b> in X x %B% : b <=> x in Q}.
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2. Considered in its functional form, f_Q is the map from X to %B%
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that is given by the following condition:
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f_Q (x) <=> x in Q.
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The "fibers" of truth and falsity under a proposition f : X -> %B%
The "fibers" of truth and falsity under a proposition f : X -> %B%
are subsets of X that are variously described as follows:
are subsets of X that are variously described as follows: