BASIC DEFINITIONS
CARTESIAN PLANE.(Link)
• Set: A set is a collection of things.
• Examples of sets are: group of
students at a school, books of a
library, models of cars, etc.
• When you cite all the elements of a set, we
say that the set has been defined by
extension.
• Example: The set formed by Pepe,
Ramón and Luis, is described like
this {Pepe, Ramón, Luis}
•Evidently, many times, it is not possible
to cite all teh elements of a set, in this
case the set is defined citing a property
that describes all the elements of a set.
Definition by comprehension.
•Example:
All
the
people
above 50 years old.
• All the members of a set are called
elements.
• A set that has no elements is called empty
set.
• Universal set or reference (is represented by
a U) is a set of which the subsets are the
possible sets of the problem.
• For example the set of natural
numbers would be the universal
set, if we are dealing with a
problem which only deals deals
with
natural
numbers.
Man
belongs to the set: mammals.
•The number of elements that a set has is
called cardinal of a set.
•Two set are the same if they are formed by
same elements.
•Subset
•A set is a subset of another, if all the
elements of this set belong to the other.
•Example: The sets A = {a, b, c,
d, e, f} and B = {a, b, c}. B is a
subset of A.
• Complemetary set
• Given that set A is a universal set U,
the complementary set (A’ with a line)
is formed by the elements of U that do
not belong with A.
• Set of the parts of the set
• Given a set A, the set formed by all the
subsets of A, is called a set of the parts
of the set.