f Boris recorded the number of daylight hours on the first day of each month in a northern hemisphere town This data was plotted

Question

f Boris recorded the number of daylight hours on the first day of each month in a northern hemisphere town This data was plotted onto a scatter diagram The points were then joined by a smooth curve with minimum point 0 8 and maximum point 6 16 as shown in the following diagram hours of daylight each day 16 12 6 9 12 month of the year Let the curve in the diagram be y f t where t is the time measured in months since Boris first recorded these values Boris thinks that f t might be modelled by a quadratic function leng a Write down one reason why a quadratic function would not be a good model for the number of hours of daylight per day across a number of years Paula thinks that a better model is f t a cos bt d t 0 for specific values of a b and d For Paula s model use the diagram to write down b the amplitude c the period d the equation of the principal axis e Hence or otherwise find the equation of this model in the form f t a cos bt d For the first year of the model find the length of time when there 10 hours and 30 minutes of daylight per day 1

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