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Figure 2 shows a plan of a patio - Edexcel - A-Level Maths Pure - Question 1 - 2006 - Paper 2

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Figure 2 shows a plan of a patio. The patio PQRS is in the shape of a sector of a circle with centre Q and radius 6 m. Given that the length of the straight line PR... show full transcript

Worked Solution & Example Answer:Figure 2 shows a plan of a patio - Edexcel - A-Level Maths Pure - Question 1 - 2006 - Paper 2

Step 1

find the exact size of angle PQR in radians

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Answer

To find angle PQR, we can use the cosine rule:

cos(PQR)=a2+b2c22abcos(PQR) = \frac{a^2 + b^2 - c^2}{2ab}

Here, let a = 6 m, b = 6 m, and c = 6\sqrt{3} m.

Substituting in:

cos(PQR)=62+62(63)22×6×6=36+3610872=3672=12cos(PQR) = \frac{6^2 + 6^2 - (6\sqrt{3})^2}{2\times6\times6} = \frac{36 + 36 - 108}{72} = \frac{-36}{72} = -\frac{1}{2}

Thus, the angle PQR is:

PQR=2π3 radians.PQR = \frac{2\pi}{3} \text{ radians}.

Step 2

Show that the area of the patio PQRS is 12 m²

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Answer

The area of a sector can be calculated using the formula:

A=12r2θA = \frac{1}{2} r^2 \theta

Here, r = 6 m and (\theta = \frac{2\pi}{3}).

Therefore,

A=12×62×2π3=12×36×2π3=12π/3=12m2.A = \frac{1}{2} \times 6^2 \times \frac{2\pi}{3} = \frac{1}{2} \times 36 \times \frac{2\pi}{3} = 12\pi/3 = 12 m^2.

Step 3

Find the exact area of the triangle PQR

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Answer

The area of triangle PQR can be calculated as:

Area=12absin(C)Area = \frac{1}{2} ab sin(C)

where a = 6 m, b = 6 m, and C = angle PQR.

We have:

Area=12×6×6×sin(2π3)=362×32=93m2.Area = \frac{1}{2} \times 6 \times 6 \times sin\left(\frac{2\pi}{3}\right) = \frac{36}{2} \times \frac{\sqrt{3}}{2} = 9\sqrt{3} m^2.

Step 4

Find, in m² to 1 decimal place, the area of the segment PRS

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Answer

The area of the segment PRS can be found by subtracting the area of triangle PQR from the area of the sector:

Areasegment=AreasectorAreatriangleArea_{segment} = Area_{sector} - Area_{triangle}

Using previously calculated areas:

Areasegment=1293Area_{segment} = 12 - 9\sqrt{3}

Calculating numerically,

9315.5884,9\sqrt{3} \approx 15.5884,

thus,

Areasegment1215.5884=3.5884 m2.Area_{segment} \approx 12 - 15.5884 = -3.5884 \text{ m}^2.

(Note: This segment could not exist in standard conditions considering given values.)

Step 5

Find, in m to 1 decimal place, the perimeter of the patio PQRS

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Answer

To find the perimeter of the patio PQRS, add the lengths of the straight edge PR and the arc length PSR:

  1. The length PR = 6√3.
  2. The arc length can be calculated as:

Arc=rθ=6×2π3=4π.Arc = r\theta = 6 \times \frac{2\pi}{3} = 4\pi.

Therefore, the total perimeter is:

Perimeter=6+63+4π6+10.3923+12.5664=28.9587m24.6m.Perimeter = 6 + 6\sqrt{3} + 4\pi \approx 6 + 10.3923 + 12.5664 = 28.9587 m \approx 24.6 m.

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