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Mike, an amateur astronomer who lives in the South of England, wants to know how the number of hours of darkness changes through the year - AQA - A-Level Maths Pure - Question 8 - 2020 - Paper 1

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Mike, an amateur astronomer who lives in the South of England, wants to know how the number of hours of darkness changes through the year. On various days between Fe... show full transcript

Worked Solution & Example Answer:Mike, an amateur astronomer who lives in the South of England, wants to know how the number of hours of darkness changes through the year - AQA - A-Level Maths Pure - Question 8 - 2020 - Paper 1

Step 1

Find the minimum number of hours of darkness predicted by Mike's model.

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Answer

To find the minimum value of H, we start by noting that the sine function varies between -1 and 1. Therefore, we can set: sin(2π(t+101.75)365)=1\text{sin}\left( \frac{2\pi(t + 101.75)}{365} \right) = -1. This gives us: Hmin=3.87(1)+11.7=11.73.87=7.83H_{min} = 3.87(-1) + 11.7 = 11.7 - 3.87 = 7.83 To convert to minutes: 7.83 hours=7 hours and 50 minutes.7.83 \text{ hours} = 7 \text{ hours and } 50 \text{ minutes}. Thus, the minimum number of hours of darkness is 7 hours and 50 minutes.

Step 2

Find the maximum number of consecutive days where the number of hours of darkness predicted by Mike's model exceeds 14.

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Answer

We need to solve the inequality: H>14H > 14 Substituting in the model: 3.87sin(2π(t+101.75)365)+11.7>143.87 \text{sin}\left( \frac{2\pi(t + 101.75)}{365} \right) + 11.7 > 14. This simplifies to: sin(2π(t+101.75)365)>1411.73.87=0.59\text{sin}\left( \frac{2\pi(t + 101.75)}{365} \right) > \frac{14 - 11.7}{3.87} = 0.59. We now find the corresponding t values. The sine function exceeds 0.59 approximately between: t1300.22,t2408.77t_1 \approx 300.22,\quad t_2 \approx 408.77 Thus, the interval of t where these conditions hold leads to: t2t1=408.77300.22108.55 days.t_2 - t_1 = 408.77 - 300.22 \approx 108.55\text{ days.}

Step 3

Explain whether Sofia's refinement is appropriate.

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Answer

Sofia's refinement, which increases the 3.87 value while keeping the other parameters constant, would increase the amplitude of the graph, thereby increasing the maximum fluctuation of hours of darkness. However, the original data suggests that this may not be necessary, as the graph of her data appears to have a lower amplitude compared to Mike's model. Hence, Sofia's refinement may not be appropriate, as it does not accurately align with the observed data, potentially leading to misleading conclusions.

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