4 . The population of wolf in a forest , w , t months after 1 April 2008 is given by w�145cos ( 0.5t� 5.2 ) � 1020 .
( a ) Find the number of wolves in the forest on 1 May 2009 , correct the answer to the nearest integer .
[ 3 ]
( b ) Find d w dt . [ 2 ]
Assume that there are 30 days per month . After n days , where n� in w attains its maximum for the first time .
( c ) Find the value of n .
, the rate of increase
[ 3 ]
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