- (a) Express \(140 \cos \theta - 480 \sin \theta\) in the form \(K \cos ( \theta + \alpha )\)
where \(K > 0\) and \(0 < \alpha < 90 ^ { \circ }\)
State the value of \(K\) and give the value of \(\alpha\), in degrees, to 2 decimal places.
A scientist studies the number of rabbits and the number of foxes in a wood for one year.
The number of rabbits, \(R\), is modelled by the equation
$$R = A + 140 \cos ( 30 t ) ^ { \circ } - 480 \sin ( 30 t ) ^ { \circ }$$
where \(t\) months is the time after the start of the year and \(A\) is a constant.
Given that, during the year, the maximum number of rabbits in the wood is 1500
(b) (i) find a complete equation for this model.
(ii) Hence write down the minimum number of rabbits in the wood during the year according to the model.
The actual number of rabbits in the wood is at its minimum value in the middle of April.
(c) Use this information to comment on the model for the number of rabbits.
The number of foxes, \(F\), in the wood during the same year is modelled by the equation
$$F = 100 + 70 \sin ( 30 t + 70 ) ^ { \circ }$$
The number of foxes is at its minimum value after \(T\) months.
(d) Find, according to the models, the number of rabbits in the wood at time \(T\) months.