2.1 Discrete-Time Signals: Time-Domain Representation Signals represented as sequences of numbers, called samples Sample value of a typical signal or sequence denoted as x[n] with n being an integer in the range-oo≤n≤∞ x[n] defined only for integer values of n and undefined for noninteger values of n Discrete-time signal represented by {x[n]}
Example 1.6. Consider the graph y(x) cos(x) over [0.0, 1.2]. (a) Use the nodes xo=0.0andx1=1.2 to construct linear interpolating polynomial Pi(). (b)Use the nodes xo 0.2 and x =1.0 to construct a linear approximating polynomial()
3.1 Discrete-Time Fourier Transform Definition- The discrete-time Fourier transform (DTFT) X(eio) of a sequence x[n] is given by jae In general,() is a complex function of the real variable and can be written as X(eio) Xre(eio) +j Xim(eio)
多元函数 定义 11.2.1 设 D 是 n R 上的点集,D 到 R 的映射 f : D →R, x 6 z 称为 n 元函数,记为 = fz x)( 。这时,D 称为 f 的定义域, f D)( = ∈ R = fzz xx ∈ D}),(|{ 称为 f 的值域,Γ= }),(|),{( 1 R ∈=∈ D + x fzz xx n 称 为 f 的图象