# I'm lost...Can someone help. No idea where to start...

• Apr 13th 2009, 04:11 PM
GlobalCooling
I'm lost...Can someone help. No idea where to start...
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

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

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

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?

Thanks a lot everyone.
• Apr 13th 2009, 04:39 PM
skeeter
Quote:

Originally Posted by 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.

.
• Apr 13th 2009, 05:08 PM
GlobalCooling
Thank you!!!
• Apr 13th 2009, 05:17 PM
Reckoner
All very good as usual, skeet, but you have an extraneous equal sign here.

Quote:

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

• Apr 13th 2009, 05:26 PM
skeeter
Quote:

Originally Posted by Reckoner
All very good as usual, skeet, but you have an extraneous equal sign here.

good eye ... my fingers are too fat.
(Wink)