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Logical Implication or Entailment

Consider

$X ⊨ y$

where $X$ represents some set of premises and y represents the conclusion. This simply means that the conjuction of all the premises entails the conclusion. We say that $X ⊨ y$ if and only if all the models of $X$ are models of $y$ .

To show $X ⊨ y$ , show that $X \Rightarrow y$ is a tautology. We call a tautology of the form $A ⊨ B$ a Logical Implication.

In predicate calculus, we use $⊢$ to denote deduction

$\nabla ⊢ Q$

where $\nabla$ represents the set of assumptions and $Q$ represents the conclusion. This expression reads " $Q$ is deduced from $\nabla$ ." If $\nabla = \emptyset$ , often denoted $⊢ Q$ , then it is call a proof. That is $Q$ is deduced soley from the axioms.

(FirstOrderMathematicalLogicAngeloMargaris)

See LogicNotes

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{{{#!latex
\section{Logical Implication or Entailment}
+= Logical Implication or Entailment =
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-\[
    X \models y
\]
where X is some set of premises and y is the conclusion. This simply means that the conjuction of all the premises entail the conclusion. We say that $X \models y$ if and only if all the models of $X$ are models of $y$.\bigskip
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-To show $X \models y$, show that $X \Rightarrow y$ is a tautology. We call a tautology of the form $A \models B$ a Logical Implication.\bigskip
+ $X ⊨ y$
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-In predicate calculus, we use $\vdash$ to denote deduction
\[
     \nabla \vdash Q
\]
where $\nabla$ is the set of assumptions and $Q$ is the conclusion is read ''$Q$ is deduced from $\nabla$.'' If $\nabla = \emptyset$, often denoted $\vdash Q$, then it is call a proof. That is $Q$ is deduced soley from the axioms. 
}}}
+where  $X$  represents some set of premises and y represents the conclusion. This simply means that the conjuction of all the premises entails the conclusion. We say that  $X ⊨ y$  if and only if all the models of  $X$  are models of  $y$ .

To show  $X ⊨ y$ , show that  $X \Rightarrow y$  is a tautology. We call a tautology of the form  $A ⊨ B$  a Logical Implication.

In predicate calculus, we use  $⊢$  to denote deduction

 $\nabla ⊢ Q$ 

where  $\nabla$  represents the set of assumptions and  $Q$  represents the conclusion. This expression reads " $Q$  is deduced from  $\nabla$ ." If  $\nabla = \emptyset$ , often denoted  $⊢ Q$ , then it is call a proof. That is  $Q$  is deduced soley from the axioms.

Diff for "LogicalImplication"

Logical Implication or Entailment