Figure 2 shows a plan view of a garden - Edexcel - A-Level Maths Pure - Question 7 - 2013 - Paper 4
Question 7
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.
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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.
Area of Triangle ABE: The formula for the area of a triangle is:
extAreaABE=21×AB×AE×sin(θ)
where ( \theta = 0.64) radians and ( AB = 23) m.
Since we first need to calculate AE using the Cosine Rule:
AE2=AB2+BE2−2(AB)(BE)cos(θ)
We find that AE is approximately 19.106 m.
Therefore, the area is:
AreaABE=21×23×19.106×sin(0.64)≈82.4m2.
Area of Sector BCDE: The formula for the area of a sector is:
extAreasector=21r2θ
where ( r = 12 ) m and ( \theta = 0.64 ) radians.
Therefore, the area of the sector is:
Areasector=21×122×0.64≈46.08m2.
Total Area of the Garden:
Total Area=AreaABE+Areasector≈82.4+46.08=128.48m2.
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.
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.
Arc Length (BCDE):
The length of the arc is calculated as: