SOLUTION: Hello, me and my friend are working on this problem and we got two answers on our calculators. It's weird because we both kept getting the same two answers. Every other time we typ

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Question 224325: Hello, me and my friend are working on this problem and we got two answers on our calculators. It's weird because we both kept getting the same two answers. Every other time we typed it in our answer would change. Here's the problem:
The traffic flow at a particular intersection is modeled by the function f defined by for What is the average rate of change of the traffic flow over the time interval 30 we set it up as:
the change in y/ the change in t =
In the end our answers were 3.817 and -.0714299
We have no clue what is right. Can you please help? Thanks in advance. =)
Found 2 solutions by jim_thompson5910, Alan3354:
Answer by jim_thompson5910(35256) (Show Source):
You can put this solution on YOUR website!
I'm assuming that you're working in radians right? If so, then...

The average should be: which approximates to 0.93546

Note: recall that the average from to is . It looks like you know the formula, but you forgot to distribute the negative through completely when it came to

Answer by Alan3354(69443) (Show Source):
You can put this solution on YOUR website!
Do you mean the interval t=30 to t=40? That's what it appears to be.
The term
should be negative.
The 25's in the NUM cancel.
--> 0.6(cos(40/3) - cos(10))
= 0.6*-0.11762...
= ~ - 0.0070577...