-16-
M13/5/MATSD/S
The depth, in metres, of water in a reservoir during a 24 day period is shown on
the graph.
The depth is modelled by f(t)=c+k sin (bt), where t is the time in days and bt is
measured in degrees.
f(t)
18
Depth (m)
12
6
0
6
12
18
24
t
Time (days)
(a) Write down the value of c.
(b) Write down the value of k.
(c) Find the value of b.
[1 mark]
[1 mark]
[2 marks]
(d) Write down the time interval for which the depth of water in the reservoir
is decreasing.
[2 marks]