SOLUTION: Please help me with the problem below: The distance y inches between a yo-yo and Susan's had at time t seconds is given by the equation y=-15cos(2(3.14)t/2.8)+15. Steven needs t

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Question 1000137: Please help me with the problem below:
The distance y inches between a yo-yo and Susan's had at time t seconds is given by the equation y=-15cos(2(3.14)t/2.8)+15. Steven needs to take a picture when the yo-yo is 7 inches from the hand and moving away from the hand. At what times can he take the picture?
Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website!
This is telling you that

Let

Using the inverse cos function
and setting for radians
on my calculator:

sec
---------------------
The cos function ( all cos functions ) begins at , then
goes to at
-----------------
My value, , is less than , so
it is on the way down from zero inches from hand to
inches from hand when cos function is zero.
When the cos is ,
yo-yo is inches from hand.
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To figure out all the times that yo-yo is in from hand
and on the way down, you must add like this:

Then you must find for , , , etc.
You will be on the way down each of those times and
in from hand
--------------------
Hope this helps