Which continuous-time signals are even functions? Which continuous-time signals are not even but can be made even by adding or subtracting a constant? Which continuous-time signals are odd functions? Which continuous-time signals are not odd but can be made odd by  adding or subtracting a constant? Which continuous-time signals have an average value of zero? Which of the continuous-time signals are square waves? What is the average signal power of x1 (t) ? What is the average signal power of x4 (t) ?