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Unformatted text preview: MATH 304, Fall 2011 Linear Algebra Homework assignment #9 (due Thursday, November 10) All problems are from Leons book (8th edition). Section 5.3: 1b, 1c, 3a, 5, 6 Section 5.4: 3b, 7c, 8a, 15b, 30 MATH 304 Linear Algebra Lecture 20: Inner product spaces. Orthogonal sets. Norm The notion of norm generalizes the notion of length of a vector in R n . Definition. Let V be a vector space. A function : V R is called a norm on V if it has the following properties: (i) ( x ) 0, ( x ) = 0 only for x = (positivity) (ii) ( r x ) =  r  ( x ) for all r R (homogeneity) (iii) ( x + y ) ( x ) + ( y ) (triangle inequality) Notation. The norm of a vector x V is usually denoted bardbl x bardbl . Different norms on V are distinguished by subscripts, e.g., bardbl x bardbl 1 and bardbl x bardbl 2 . Examples. V = R n , x = ( x 1 , x 2 , . . . , x n ) R n . bardbl x bardbl = max(  x 1  ,  x 2  , . . . ,  x n  ). bardbl x bardbl p = (  x 1  p +  x 2  p + +  x n  p ) 1 / p , p 1. Examples. V = C [ a , b ], f : [ a , b ] R . bardbl f bardbl = max a x b  f ( x )  . bardbl f bardbl p = parenleftbiggintegraldisplay b a  f ( x )  p dx parenrightbigg 1 / p , p 1. Normed vector space Definition. A normed vector space is a vector space endowed with a norm. The norm defines a distance function on the normed vector space: dist ( x , y ) = bardbl x y bardbl . Then we say that a sequence x 1 , x 2 , . . . converges to a vector x if dist ( x , x n ) 0 as n . Also, we say that a vector x is a good approximation of a vector x if dist ( x , x ) is small. Inner product The notion of inner product generalizes the notion of dot product of vectors in R n . Definition. Let V be a vector space. A function : V V R , usually denoted ( x , y ) = ( x , y ) , is called an inner product on V if it is positive, symmetric, and bilinear. That is, if (i) ( x , x ) 0, ( x , x ) = 0 only for x = (positivity) (ii) ( x , y ) = ( y , x ) (symmetry) (iii) ( r x , y ) = r ( x , y ) (homogeneity) (iv) ( x + y , z ) = ( x , z ) + ( y , z ) (distributive law) An inner product space is a vector space endowed with an inner product. Examples. V = R n ....
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 Spring '08
 HOBBS
 Linear Algebra, Algebra

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