The number of times that the fan rotate each minute is: 1,000 times.
Given:
y = Equals 6 cosine (2,000 pi x) + 11
Where x is time in minutes.
Hence:
Using cosine function:
y = a·cos(b·x - c) + d
Where:
b = 2,000·pi
a = 6
c/b =horizontal shift
While, period (p)
p = 2·pi/b
Hence:
p = 2·pi/(2,000·pi)
p = 1/1,000
p = 0.001 minutes per revolution
rpm = 1/p
rpm= 1/(0.001) ×1/minutes)
rpm= 1,000 times per minutes
Therefore the correct option is A.
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