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A well-formed formula is any atomic formula, or any formula that can be built up from atomic formulas by means of operator symbols according to the rules of the grammar. The language L {\displaystyle {\mathcal {L}}} , then, is defined either as being identical to its set of well-formed formulas, [ 48 ] or as containing that set (together with ...
In propositional logic, a propositional formula is a type of syntactic formula which is well formed. If the values of all variables in a propositional formula are given, it determines a unique truth value. A propositional formula may also be called a propositional expression, a sentence, [1] or a sentential formula.
If is a set, then there exists precisely one function from to , the empty function. As a result, the empty set is the unique initial object of the category of sets and functions. The empty set can be turned into a topological space , called the empty space, in just one way: by defining the empty set to be open .
If a function f is real-valued, then the limit of f at p is L if and only if both the right-handed limit and left-handed limit of f at p exist and are equal to L. [27] The function f is continuous at p if and only if the limit of f(x) as x approaches p exists and is equal to f(p).
The solutions of the quadratic equation ax 2 + bx + c = 0 correspond to the roots of the function f(x) = ax 2 + bx + c, since they are the values of x for which f(x) = 0. If a , b , and c are real numbers and the domain of f is the set of real numbers, then the roots of f are exactly the x - coordinates of the points where the graph touches the ...
The material conditional (also known as material implication) is an operation commonly used in logic.When the conditional symbol is interpreted as material implication, a formula is true unless is true and is false.
The formulas will be certain expressions (that is, strings of symbols) over this alphabet. The formulas are inductively defined as follows: Each propositional variable is, on its own, a formula. If φ is a formula, then ¬φ is a formula. If φ and ψ are formulas, and • is any binary connective, then ( φ • ψ) is a formula.
It follows that the solutions of such an equation are exactly the zeros of the function . In other words, a "zero of a function" is precisely a "solution of the equation obtained by equating the function to 0", and the study of zeros of functions is exactly the same as the study of solutions of equations.