Edexcel
C3
2010
June
Q2
7 marks
Moderate -0.3
2. A curve \(C\) has equation
$$y = \frac { 3 } { ( 5 - 3 x ) ^ { 2 } } , \quad x \neq \frac { 5 } { 3 }$$
The point \(P\) on \(C\) has \(x\)-coordinate 2. Find an equation of the normal to \(C\) at \(P\) in the form \(a x + b y + c = 0\), where \(a , b\) and \(c\) are integers.
Edexcel
C3
2010
June
Q7
15 marks
Standard +0.3
7. (a) Express \(2 \sin \theta - 1.5 \cos \theta\) in the form \(R \sin ( \theta - \alpha )\), where \(R > 0\) and \(0 < \alpha < \frac { \pi } { 2 }\).
Give the value of \(\alpha\) to 4 decimal places.
(b) (i) Find the maximum value of \(2 \sin \theta - 1.5 \cos \theta\).
(ii) Find the value of \(\theta\), for \(0 \leqslant \theta < \pi\), at which this maximum occurs.
Tom models the height of sea water, \(H\) metres, on a particular day by the equation
$$H = 6 + 2 \sin \left( \frac { 4 \pi t } { 25 } \right) - 1.5 \cos \left( \frac { 4 \pi t } { 25 } \right) , \quad 0 \leqslant t < 12$$
where \(t\) hours is the number of hours after midday.
(c) Calculate the maximum value of \(H\) predicted by this model and the value of \(t\), to 2 decimal places, when this maximum occurs.
(d) Calculate, to the nearest minute, the times when the height of sea water is predicted, by this model, to be 7 metres.