Question 867243
Write a cosine function with the given amplitude, period, and vertical shift. 
amplitude: 2
period: 2/3pi
vertical shift: -1
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Form of equation for cos function: y=Acos(Bx-C)+D, Amplitude=A, Period=2π/B, Phase shift=C/B, D=Vertical shift
For given problem:
Amplitude,A=2
Period=2π/3=2π/B
B=3
C=0
D=-1
Equation: y=2cos(3x)-1