The cosine equation of the function should be [tex]y = 7\cos (x - \frac{\pi}{4}) - 4[/tex]
Calculation of cosine equaton:
Since
y = A cos (Bx - C) + D
A (amplitude) = max - D
B = Period/2[tex]\pi[/tex] = Period represent the distance from max to next max
C = B · Phase Shift = Phase shift is distance from y-axis to max
D (vertical shift) =[tex](max + min)\div 2[/tex]
So,
D [tex]= (max + min)\div 2 = (3 - 11)\div 3[/tex] = -4
A = max - D = 3 - (-4) = 7
Period = [tex]9\pi \div 4 - \pi \div 4 = 8\pi \div 4 = 2\pi[/tex]
B = [tex]Period\div 2\pi = 2\pi\div 2\pi[/tex] = 1
Phase Shift = [tex]\pi \div 4 - 0 = \pi \div 4[/tex]
C = B · Phase Shift = [tex]1. \pi \div 4 = \pi \div 4[/tex]
So, the above equation should be considered.
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