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Mathematics1 Mathematics 1 Applied Informatics Štefan BEREŽNÝ

6 th lecture

MATHEMATICS 1 Applied Informatics 3 Štefan BEREŽNÝ Contents LINEAR ALGEBRA Vector Space n-dimensional Arithmetic Vector Space Basis Dimension

MATHEMATICS 1 Applied Informatics 4 Štefan BEREŽNÝ Vector Space Definition: The nonempty set V with the operations “addition” and “multiplication by real numbers”, which satisfy following conditions: (1)  u, v  V : u + v  V (i. e. V is closed with respect to operation “addition”) (2)  u  V,    R  u  V (i. e. V is closed with respect to operation “multiplication”)

MATHEMATICS 1 Applied Informatics 5 Štefan BEREŽNÝ Vector Space (3)  u, v  V : u + v = v + u (4)  u, v, w  V :( u + v ) + w = v + ( u + w ) (5)  u  V : 1  u = u (6)  u  V,  ,   R:  (  u ) = (  )  u (7)  u, v  V,    R:  ( u + v ) =  u +  v (8)  u  V,  ,   R: (  +  )  u =  u +  u

MATHEMATICS 1 Applied Informatics 6 Štefan BEREŽNÝ Vector Space (9)There exists a so called zero vector o = (0, 0, …, 0) in V. If u is any vector from V then: u + o = u (10)To every vector u  V there exists a vector  u (vector  u a so called opposite vector to vector u so that: u + (  u ) = o

MATHEMATICS 1 Applied Informatics 7 Štefan BEREŽNÝ Vector Space is called vector space. The elements are called vectors. If V = R n (R n is set of all n -tuples of real numbers) then the set V is called the n -dimensional arithmetic space. Its elements ( n -tuples of real numbers) are called arithmetic vectors.

MATHEMATICS 1 Applied Informatics 8 Štefan BEREŽNÝ Vector Space Theorem: (Uniqueness of the zero vector) Let V is the vector space. There exists only one zero vector in the vector space V. Theorem: Let V is the vector space. For any vector u  V and any real number   R, it holds: (a)0  u = o (b)(  1)  u =  u (c)  o = o

MATHEMATICS 1 Applied Informatics 9 Štefan BEREŽNÝ Vector Space Definition: If u 1, u 2, …, u n is a group of vectors in the vector space V and  1,  2, …,  n are real numbers then the vector v  V : v =  1  u 1 +  2  u 2 +  3  u 3 + … +  n  u n is called the linear combination of the vectors u 1, u 2, …, u n.

MATHEMATICS 1 Applied Informatics 10 Štefan BEREŽNÝ Vector Space Definition: If all coefficient  1,  2, …,  n are zero then it is called trivial linear combination. If there exists coefficient  1,  2, …,  n such that at least one of them is different from zero then it is called non-trivial linear combination.

MATHEMATICS 1 Applied Informatics 11 Štefan BEREŽNÝ Vector Space Definition: The group of vectors u 1, u 2, …, u n is called linearly dependent if there exists non-trivial linear combination such that  1  u 1 +  2  u 2 +  3  u 3 + … +  n  u n = o. A group of vectors u 1, u 2, …, u n which is not linearly dependent is called linearly independent.

MATHEMATICS 1 Applied Informatics 12 Štefan BEREŽNÝ Vector Space Theorem: If one of the vectors u 1, u 2, …, u n in the vector space V is equal to the zero vector then the group of vectors u 1, u 2, …, u n is linearly dependent.

MATHEMATICS 1 Applied Informatics 13 Štefan BEREŽNÝ Vector Space Theorem: The group of vectors u 1, u 2, …, u n from the vector space V, where n  1, is linearly dependent if and only if at least one vector from this group can be expressed as a linear combination of the other vectors of the group.

MATHEMATICS 1 Applied Informatics 14 Štefan BEREŽNÝ Vector Space Theorem: The group of vectors u 1, u 2, …, u n from the vector space V is linearly independent if and only if the vector equation  1  u 1 +  2  u 2 +  3  u 3 + … +  n  u n = o has only the zero (trivial) solution  1 = 0,  2 = 0,  3 = 0, …,  n = 0.

MATHEMATICS 1 Applied Informatics 15 Štefan BEREŽNÝ Vector Space Theorem: Let u 1, u 2, …, u n be a linearly dependent group of vectors from the vector space V. Then every group of vectors from vector space V which contains the vectors u 1, u 2, …, u n is also linearly dependent.

MATHEMATICS 1 Applied Informatics 16 Štefan BEREŽNÝ Vector Space Definition: Let the group of vectors u 1, u 2, …, u n is from the vector space V. We say that the set of vectors B = =  u 1, u 2, …, u n  is basis of the vector space V if: (a)the group of vectors u 1, u 2, …, u n is linearly independent (b)the group of vectors u 1, u 2, …, u n generate the vector space V.

MATHEMATICS 1 Applied Informatics 17 Štefan BEREŽNÝ Vector Space Definition: Let n be a natural number. We say that the vector space V is n-dimensional or equivalently: its dimension is equal to n (we write dim( V ) = n ) if cardinality of basis of the vector space V is equal n.

MATHEMATICS 1 Applied Informatics 18 Štefan BEREŽNÝ Vector Space Theorem: Let u 1, u 2, …, u n be a basis of the vector space V. Then every vector from V can be uniquely expressed as a linear combination of the vectors u 1, …, u n. If the vector space V is n -dimensional then there exists a group of n vectors in V (basis) which is linearly independent and each group of more then n vectors from V is linearly dependent.

MATHEMATICS 1 Applied Informatics 19 Štefan BEREŽNÝ Vector Space Theorem: Suppose that W is a subset of vector space V. If W is the vector space with the same operations “addition” and “multiplication by real numbers” as in vector space V then we call the set W the subspace of the vector space V.

MATHEMATICS 1 Applied Informatics 20 Štefan BEREŽNÝ Thank you for your attention.

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