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Unformatted text preview: Lecture Note 4: Sept 25  29, 2006 Dr. Jeff ChakFu WONG Department of Mathematics Chinese University of Hong Kong jwong@math.cuhk.edu.hk MAT 2310 Linear Algebra and Its Applications Fall, 2006 Produced by Jeff ChakFu WONG 1 MATRIX TRANSFORMATIONS Our aim is to • study the notation R n for the set of all nvectors with real entries. • study the elements in R 2 and R 3 geometrically as directed line segments in a rectangular coordinate system. nvector : A 1 × n or an n × 1 matrix is called an nvector. When n is understood, we refer to nvectors only as vectors. nspace : The set of all nvectors is called nspace. For vectors whose entries are real numbers we denote nspace as R n . MATRIX TRANSFORMATIONS 2 The vector x = x y in R 2 is represented by the directed line segment shown in Figure 1(a). The vector x = x y z in R 3 is represented by the directed line segment shown in Figure 1(b). MATRIX TRANSFORMATIONS 3 O x y y  axis (x,y) x x  axis (a) x (x, y, z) x  z  y  axis axis axis O y x z (b) Figure 1: MATRIX TRANSFORMATIONS 4 Example 1 Figure 2(a) shows geometric representations of the 2vectors u 1 = 1 2 , u 2 =  2 1 and u 3 = 1 in a twodimensional rectangular coordinate system . Figure 2(b) shows geometric representations of the 3vectors v 1 = 1 2 3 , v 2 =  1 2 2 and v 3 = 1 in a threedimensional rectangular coordinate system . MATRIX TRANSFORMATIONS 5 u u x y 2 O 1 1 2 u 1 2 3 (a) O y z x v v v 3 1 2 (b) Figure 2: MATRIX TRANSFORMATIONS 6 Our aim here is: • to give a short introduction from a geometrical point of view to certain functions mapping R n into R m . • to study the socalled matrix transformation . Here we only consider the situation where m and n have values 2 or 3. MATRIX TRANSFORMATIONS 7 Things to remember : A function is a rule that assigns to each element of one set exactly one element of another set. Definition: A transformation L of R n into R m , written L : R n → R m , is a rule that assigns to each vector u in R n a unique vector v in R m . 1. R n is called the domain of L . 2. R m is the codomain . 3. We write L ( u ) = v ; (a) v is called the image of u under L . (b) The set of all images is called the range of L . • The range may be used the whole of R n or only part of it. 4. The terms mapping and functions are also used for transformation. MATRIX TRANSFORMATIONS 8 • If A is an m × n matrix and u is an nvector, then the matrix product A u is an mvector. • A function f mapping R n into R m is denoted by f : R n → R m ....
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This note was uploaded on 10/15/2009 for the course MATHEMATIC MAT2310B taught by Professor Jeffwong during the Spring '09 term at CUHK.
 Spring '09
 JeffWong
 Linear Algebra, Algebra, Transformations

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