Calculating Average Temperature Using Integrals

[badtwistoffate]

A certain city, the temp in degrees Farenheit, t hrs after 9 am was modeled by the function: T(t)=50 + 14 sin (Pi t / 12)
Find avg temp during the period from 9 am to 9 pm.

What i did was take the Int[50 + 14 sin (Pi t / 12),t,0,9]... but this doesn't produce the answer. It says model after 9 am so at 9=0 for a , b = 10 for 9pm?
Any help?

 

[mathmike]

shouldnt b be 12 and not 10 since it is 12 hours from 9am - 9pm

 

[Fermat]

Set your limits a,b to a = 9 and b = 21 (using 24-hr notation)

 

[badtwistoffate]

i tried 9 to 21 and it didnt work before...

 

[badtwistoffate]

it works from 0 to 12, thanks, don't know why i thought 10 DUH