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Figure 2 shows a plan view of a garden - Edexcel - A-Level Maths Pure - Question 7 - 2013 - Paper 4

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Figure 2 shows a plan view of a garden. The plan of the garden ABCDEA consists of a triangle ABE joined to a sector BCDE of a circle with radius 12 m and centre B. T... show full transcript

Worked Solution & Example Answer:Figure 2 shows a plan view of a garden - Edexcel - A-Level Maths Pure - Question 7 - 2013 - Paper 4

Step 1

a) the area of the garden, giving your answer in m², to 1 decimal place.

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Answer

To find the area of the garden, we need to calculate the area of triangle ABE and the area of sector BCDE.

  1. Area of Triangle ABE: The formula for the area of a triangle is:

    extAreaABE=12×AB×AE×sin(θ) ext{Area}_{ABE} = \frac{1}{2} \times AB \times AE \times \sin(\theta) where ( \theta = 0.64) radians and ( AB = 23) m.

    Since we first need to calculate AE using the Cosine Rule:

    AE2=AB2+BE22(AB)(BE)cos(θ) AE^2 = AB^2 + BE^2 - 2(AB)(BE)\cos(\theta) We find that AE is approximately 19.106 m.

    Therefore, the area is:

    AreaABE=12×23×19.106×sin(0.64)82.4m2.\text{Area}_{ABE} = \frac{1}{2} \times 23 \times 19.106 \times \sin(0.64) \approx 82.4 m^2.

  2. Area of Sector BCDE: The formula for the area of a sector is:

    extAreasector=12r2θ ext{Area}_{sector} = \frac{1}{2} r^2 \theta where ( r = 12 ) m and ( \theta = 0.64 ) radians.

    Therefore, the area of the sector is:

    Areasector=12×122×0.6446.08m2.\text{Area}_{sector} = \frac{1}{2} \times 12^2 \times 0.64 \approx 46.08 m^2.

  3. Total Area of the Garden:

    Total Area=AreaABE+Areasector82.4+46.08=128.48m2.\text{Total Area} = \text{Area}_{ABE} + \text{Area}_{sector} \approx 82.4 + 46.08 = 128.48 m^2.

Thus rounding to 1 decimal place, the area is:

Answer: The area of the garden is approximately 128.5 m².

Step 2

b) the perimeter of the garden, giving your answer in metres, to 1 decimal place.

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Answer

To calculate the perimeter of the garden, we sum the lengths of all the sides: AB, BE, AE and the arc BCDE.

  1. Segment Lengths:

    • AB = 23 m
    • BC = 12 m
    • AE can be calculated from the triangle using the earlier derived value.
    • BE can be found as:

    BE=r=12m.BE = r = 12 m.

  2. Arc Length (BCDE): The length of the arc is calculated as:

    extArcLength=r×θ=12×0.64=7.68m. ext{Arc Length} = r \times \theta = 12 \times 0.64 = 7.68 m.

  3. Total Perimeter:

    Perimeter=AB+BC+AE+BE+Arc Length=23+12+19.106+12+7.68.\text{Perimeter} = AB + BC + AE + BE + \text{Arc Length} = 23 + 12 + 19.106 + 12 + 7.68.

Thus, the total perimeter is approximately:

Perimeter73.786m.\text{Perimeter} \approx 73.786 m.

Rounding to 1 decimal place, the perimeter is:

Answer: The perimeter of the garden is approximately 73.8 m.

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