Asked by megan

The monthly sales S (in hundreds of units) of baseball equipment for an Internet sporting goods site are approximated by
S = 60.1 − 43.9 cos πt/ 6
where t is the time (in months), with t = 1 corresponding to January. Determine the months when sales exceed 7700 units at any time during the month.
Answered by Reiny
60.1 − 43.9 cos πt/ 6 ≥ 77
− 43.9 cos πt/ 6 ≥ 16.9

cos πt/6 ≤ - .38496...

consider cos πt/6 = - .38496...
I know cos 1.1756.. = +.38496

so πt/6 = π - 1.1756 = appr 1.966
t = 3.755

or

πt/6 = π + 1.1756.. = 4.3172..
t = 8.245

draw you conclusion regarding the month

verification by Wolfram:
http://www.wolframalpha.com/input/?i=solve+y+%3D+60.1+%E2%88%92+43.9+cos+(%CF%80t%2F6)+,+y+%3D+77

look at the graph for t ≥ 0 at the first intersection

Answered by megan
the months are

a. march through september
b. april through august
c. march through august
d. may through september
e. april through august

i think the answer is c
Answered by megan
is c the correct answer?
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