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Unformatted text preview: Lecture Note 15 Dr. Jeff ChakFu WONG Department of Mathematics Chinese University of Hong Kong [email protected] MAT 2310 Linear Algebra and Its Applications Fall, 2007 Produced by Jeff ChakFu WONG 1 D OT P RODUCT IN R n DOT PRODUCT IN R n 2 n VECTORS In this note we shall focus on nvectors from a geometrical point of view by generalizing the notations discussed in the preceding section. nVECTORS 3 As we have already seen in the first part of Lecture note 1, an n × 1 matrix u = u 1 u 2 . . . u n n × 1 , where u 1 ,u 2 ,...,u n are real numbers, which are called the components of u . Since an nvector is an n × 1 matrix, the nvectors u = u 1 u 2 . . . u n , v = v 1 v 2 . . . v n are said to be equal if u i = v i (1 ≤ i ≤ n ) . nVECTORS 4 Example 1 The 4vectors 1 2 3 4 and 1 2 3 4 are not equal, since their fourth components are not the same. nVECTORS 5 The set of all nvectors is denoted by R n and is called nspace . As the actual value of n need to be addressed, we regard to nvectors simply as vectors . The real numbers are called scalars . The components of a vector are real numbers and hence the components of a vector are scalars. nVECTORS 6 V ECTOR O PERATIONS Definition: Let u = u 1 u 2 . . . u n , and v = v 1 v 2 . . . v n be two vectors in R n . The sum of the vectors u and v is the vector u + v = u 1 + v 1 u 2 + v 2 . . . u n + v n and it is denoted by u + v . VECTOR OPERATIONS 7 Example 2 If u = 1 2 3 and v = 2 3 3 are vectors in R 3 , then u + v = 1 + 2 2 + 3 3 + ( 3) = 3 1 . VECTOR OPERATIONS 8 Definition: If u = u 1 u 2 . . . u n is a vector in R n and c is a scalar, then the scalar multiple c u of u by c is the vector u = c u 1 c u 2 . . . c u n . VECTOR OPERATIONS 9 Example 3 If u = 2 3 1 2 is a vector in R 4 and c = 2 , then c u = 2 2 3 1 2 =  4 6 2 4 ....
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This note was uploaded on 05/18/2010 for the course MATHEMATIC MAT2310 taught by Professor Dr.jeffchakfuwong during the Spring '06 term at CUHK.
 Spring '06
 Dr.JeffChakFuWONG
 Linear Algebra, Algebra

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