Question 1108331:  What is the equation of a cosine function with an amplitude of 4, a period of 3pi, a horizontal phase shift of pi/4 to the right, and a vertical shift down of 3 units? 
 Answer by greenestamps(13215)      (Show Source): 
You can  put this solution on YOUR website! 
  
The general form of a cosine function is
  
 
  
In this form, |a| is the amplitude, c is the (horizontal) phase shift, and d is the vertical shift.
  
Note that in this form, the coefficient of x must be 1, in order for c to be the correct phase shift.
  
For b in the formula, you have to do a bit of work: b is   where p is the period.
  
So in your example, a = 4, b = (2pi)/3pi) = 2/3, c = pi/4, and d = -3.
  
  
  | 
 
  
 
 |   
 
 |