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**GlobalCooling** For the 18 hour time period beginning at midnight, the temperature F (in degress Fahrenheit) in a particular room is given by the function F(t)=-12sin(t/3)+78, where t is measured in hours

a. To the nearest degree, what is the temperature at 9 AM

evaluate F(9)

b. During which two consecutive hours does the temperature reach a maximum?

max temp will be when sin(t/3) = -1 (why?) ... sin(what values) = -1 ?

c. To the nearest tenth, what is the average temperature for the 18 hour period?

remember this ?

$\displaystyle \textcolor{red}{\frac{1}{b-a} \int_a^b F(t) \, dt}$

d. If the air conditioning turns on when the temperature is 83 degrees or higher, at what time interval(s) is the air conditioning operating?

solve for the intervals when $\displaystyle \textcolor{red}{F(t) \geq 83}$

Thanks a lot everyone.