SIGNALS AND SYSTEMS ( a ) x(r - 2 ) is sketched in Fig. 1-18(a). ( 6 ) x ( 2 0 is sketched in Fig. 1-18(b). ( c ) x(t/2) is sketched in Fig. 1-18(c). ( d ) X ( - t ) is sketched in Fig. 1-1Nd). (c) F g 1-18 i. 1.2. A discrete-time signal x [ n ] is shown in Fig. 1-19. Sketch and label each of the following signals. ( a ) x [ n - 21; ( b ) x [ 2 n ] ; ( c ) x[-n]; (d) x[-n + 21 F g 1-19 i. .CHAP. 11 SIGNALS AND SYSTEMS (a) (b) (c)...