Answer#2
According to the description given,
the graph of 


lies between the lines 


and 


.
It crosses the y-axis at 


, rises up to 5 then goes down to 1 and
finally back up to 2 at 


.
Such a graph with the same basic shape as a sine graph is shown below.

To get an equation
for this, of the form 


,
we might start by noticing that the constant m is midway between the extremes – i.e. at 


,
and that the amplitude R is half of
the total range – i.e. 


.
For the period to be 6, we need 


.
So 


giving 


.
Finally, to determine s, we use the
fact that the y-intercept is 2. This gives 


,
so 


.
From the picture on the right we see that there are two points
corresponding to 


.
At Q
, 


,
and at P, 



But, at Q,
increasing t reduces y.
So, since f(t) is increasing at 


,
s must correspond to point P.
So 


will do, and 


.