SOLUTION: Outside temperature over a day can be modeled as a sinusoidal function. Suppose you know the high temperature of 96 degrees occurs at 4 PM and the average temperature for the day i

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Question 1176031: Outside temperature over a day can be modeled as a sinusoidal function. Suppose you know the high temperature of 96 degrees occurs at 4 PM and the average temperature for the day is 85 degrees. Find the temperature, to the nearest degree, at 7 AM.
Answer by ikleyn(52790) About Me  (Show Source):
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Outside temperature over a day can be modeled as a sinusoidal function.
Suppose you know the high temperature of 96 degrees occurs at 4 PM and
the average temperature for the day is 85 degrees.
Find the temperature, to the nearest degree, at 7 AM.
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Our 24-hour cycle of the daily temperature change starts at 4 pm, when the temperature is maximal.


So, our sinusoidal function is, actually, the cosine function, if to start counting time from 4 pm = 16:00, or


    T(t) = T%5Bav%5D + %28T%5Bmax%5D-T%5Bav%5D%29%2Acos%28%282pi%2A%28t-16%29%2F24%29%29


where "t" is the local astronomic time in the 24-hours "military" time scale in your watch.



At 7 am next day, we have  5%2F8 of the full cycle elapsed.


It corresponds to  5pi%2F4  on the unit circle, and  cos%285pi%2F4%29 = - sqrt%282%29%2F2.


So, the temperature at 7 am  next day will be  


    85%5Eo+%2B+%2896%5Eo-85%5Eo%29%2Acos%285pi%2F4%29 = 85%5Eo+-+11%5Eo%2A%28sqrt%282%29%2F2%29 = 85° - 0.707*11° = 77.2°.


ANSWER.  We can expect  77.2°, or 77° rounded at 7 am next day.

Solved.