Question 910139
How to find the amplitude and period.
y = -4 cos 1/2 x 
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Equation for cos function: y=Acos(Bx-c), A=amplitude,period=2π/B
For given function:
y=-4cos(x/2)
amplitude=4
B=1/2
period=2π/B=2π/(1/2)=4π