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--- assignments:a1 [2012/09/09 21:47] – marash
+++ assignments:a1 [2013/09/04 21:19] (current) – marash
@@ Line 17: / Line 17: @@
 Problem 1.15 (i) and (iii)
+**Hints for Problem 1.5 part (v)**
+Note that:
+  - All CT complex exponentials are periodic.
+  - A real valued exponential signal is not periodic.
+  - Sum of a periodic signal and an aperiodic signal is not periodic.
+**Hints for Problem 1.5 part (vi)**
+Note that:
+  - Sum of a periodic signal and an aperiodic signal is not periodic.
+  - Product of two periodic signals is not necessarily periodic.
+  - If we have y(t) = x_1(t)+x_2(t)+x_3(t) where all three are periodic with periods T_1, T_2, and T_3 respectively, then y(t) is periodic if all combinations of T_1/T_2, T_1/T_3, and T_2/T_3 are rational numbers.
+  - Use the following identities to simplify the function:
+  * sin^2(t) = 1/2(1 − cos(2t))
+  * cos(a)cos(b) = 1/2[cos(a+b) + cos(a−b)]
+**Problem 1.15**
+There is a typo and the correct one is as follows:
+x1[k] = sin(4k)+cos(2*pi*k/3).