SOLUTION: Hello, I need help on this question please : A Canada Post outlet in small Alberta town found that the number of pieces of mail received per week, m, can be modelled by the fun

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Question 1072934: Hello, I need help on this question please :
A Canada Post outlet in small Alberta town found that the number of pieces of mail received per week, m, can be modelled by the function
m (t) = 3200 cos(0.72 t - 1.15) + 6400
Where t is the number of years since January 1,2005
For how many of the first 10 years, to the nearest tenth of a year did the Canada Post outlet receive fewer than 6600 pieces of mail per week?
This falls within trigonometry function and graphing. I tried the question by plugging in 10 for t and 6600 for m(t) and got 0.7
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
No, you need to find when the value of the function was less than 6600.
m%28t%29%3C6600
3200cos%280.72t-1.15%29%2B6400%3C6600
3200cos%280.72t-1.15%29%3C200
cos%280.72t-1.15%29%3C0.0625
So find the times when the value of the cosine function is equal to 0.0625,
0.72t-1.15=1.5083
0.72t=2.658
t=3.692
and
0.72t-1.15=4.775
0.72t=5.925
t=8.229
.
.
.
.
.
.
.
So between t=3.7 years and t=8.2 years, the number of pieces of mail fell below 6600.