A digital delay device echoes an input signal by repeating it a fixed length of time after it is received. If such a device receives the pure note f1(t)= 5sint and echoes the pure note f2(t)= 5cost, then the combined sound is f(t) = f1(t) + f2(t). Required:
a. Graph y= f(t) and observe that the graph has the form of a sine curve y= ksin(t+ φ).
b. Find k and φ.