Logs and lg in logarithms both read làge；; ; Ln in logarithm is pronounced làoin. Logarithm is the reciprocal of power just as division is the reciprocal of multiplication, and vice versa. This means that the logarithm of a number is the logarithmic counting factor in the multiplier, and it must produce another index with a fixed number as the base.

formula

General format, expressed by mathematical symbols, the formula of a certain relationship between various quantities (such as laws or theorems) can be applied to the methods of similar things.

Formulas, in mathematics, physics, chemistry, biology and other natural sciences, use mathematical symbols to express the relationship between several quantities. It is universal and applicable to all similar problems. In mathematical logic, a formula is a formal grammatical object to express a proposition, but the proposition may depend on the free variable value of the formula.

The exact definition of a formula depends on the specific formal logic involved, but there is a very typical definition for first-order logic, and the formula is defined relative to a specific language. That is, a set of constant symbols, function symbols and relational symbols, in which each function and relational symbol has an argument arity to indicate the number of parameters it accepts.

basic requirement

According to the semantic inference rules of predicate logic, semantics should be consistent, that is, for a propositional logic statement set F, if and only if there is an explanation that at least all elements of F are true under I, then F is semantically consistent. In propositional logic semantics, an assignment cannot give a propositional atomic formula both truth and false.

In propositional logic semantics, under the same interpretation, a set cannot belong to both the extension of a predicate and the extension of this predicate.

related notion

Of all the line segments with one point, only one straight line and one point outside the known straight line and connected with all points on the straight line, the vertical line segment is the shortest.

The axiom of parallelism passes through a point outside a straight line, and one and only one straight line is parallel to this straight line. If both lines are parallel to the third line, the two lines are also parallel to each other.

The congruence angle is equal, the internal angle of two parallel lines is equal, the two parallel lines are complementary to the side internal angle, and the two parallel lines are parallel.