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The diagram shows three circles, each of radius 4 cm - Edexcel - GCSE Maths - Question 1 - 2022 - Paper 2

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The diagram shows three circles, each of radius 4 cm. The centres of the circles are A, B and C such that ABC is a straight line and AB = BC = 4 cm. Work out the t... show full transcript

Worked Solution & Example Answer:The diagram shows three circles, each of radius 4 cm - Edexcel - GCSE Maths - Question 1 - 2022 - Paper 2

Step 1

Find the area of the segment (for circle A)

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Answer

To find the area of one shaded segment in circle A, we first need to determine the angle of the sector formed at center A. Since AB = BC = 4 cm and the radius of the circles is also 4 cm, triangle ABC is isosceles with sides AB and AC equal. The angle at A can be found using the cosine rule or recognizing symmetry.

The angle at A is 120 degrees (as angle B is formed by the two radii).

The area of the sector of circle A can be calculated as:

Area of sector=120360×πr2=13×π×42=163π\text{Area of sector} = \frac{120}{360} \times \pi r^2 = \frac{1}{3} \times \pi \times 4^2 = \frac{16}{3} \pi

Next, we find the area of triangle ABC:

Area of triangle=12×base×height\text{Area of triangle} = \frac{1}{2} \times base \times height

For triangle ABC, the height can be calculated by using trigonometry, which gives the height as: h=4×sin(60)=4×32=23h = 4 \times \sin(60^\circ) = 4 \times \frac{\sqrt{3}}{2} = 2\sqrt{3}

Thus, the area of triangle ABC is:

Area of triangle=12×4×23=43\text{Area of triangle} = \frac{1}{2} \times 4 \times 2\sqrt{3} = 4\sqrt{3}

Therefore, the area of the shaded segment in circle A is:

Area of segment=Area of sectorArea of triangle=163π43\text{Area of segment} = \text{Area of sector} - \text{Area of triangle} = \frac{16}{3}\pi - 4\sqrt{3}

Step 2

Find the area of the segment (for circle C)

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Answer

Using the same approach for circle C, we again have an angle of 120 degrees at center C.

Thus, the area of the sector in circle C is equal to that of circle A:

Area of sector for circle C=163π\text{Area of sector for circle C} = \frac{16}{3} \pi

And the area of triangle ABC remains unchanged:

Area of triangle=43\text{Area of triangle} = 4\sqrt{3}

The area of the shaded segment in circle C is also:

Area of segment for C=163π43\text{Area of segment for C} = \frac{16}{3}\pi - 4\sqrt{3}

Step 3

Combine the areas of the shaded segments

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Answer

To find the total area of the two shaded regions, we sum the areas of the segments from circles A and C:

Total shaded area=2(163π43)\text{Total shaded area} = 2 \left( \frac{16}{3}\pi - 4\sqrt{3} \right)

This simplifies to:

Total shaded area=323π83\text{Total shaded area} = \frac{32}{3}\pi - 8\sqrt{3}

Thus, the final answer for the total area of the two shaded regions in terms of π is:

323π83 cm2\frac{32}{3} \pi - 8 \sqrt{3} \text{ cm}^2

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