**for the function given, state the middle line : f(t)= 40cos (80t + 20)**

**Answer:**

The amplitude is 40 since y=Acos(B) +C has amplitude A and vertical shift C. The vertical shift is C=0 and B =80t+20 is related to horizontal frequency and shift. This means the graph of the cosine will oscillate between -40 and 40. The middle line will therefore be the line y=0.