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| 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(13209)
      (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.
 
 
  
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