GCSE 995381
IGCSE PASTE
NOT TO
SCALE
Past Papers
8 cm
30°
A
OAB is the sector of a circle, centre 0, with radius 8 cm and sector angle 30°.
BC is perpendicular to OA.
Calculate the area of the region shaded on the diagram.

Respuesta :

Answer:

[tex]2.9 cm^2[/tex]

Step-by-step explanation:

Given,

Angle of sector = 30°

Radius of circle, r = 8 cm

Area of the shaded region, A =?

The diagram is attached below.

Now,

Area of shaded region = Area of sector - Area of triangle

Area of triangle = [tex]\frac{1}{2}\times base \times height[/tex]

We know that,

[tex]\sin \theta = \dfrac{P}{H}[/tex]

[tex]\sin 30^\circ= \dfrac{P}{8}[/tex]

[tex]P = \dfrac{8}{2}[/tex]

[tex]P = 4\ cm[/tex]

And

[tex]\cos \theta =\dfrac{B}{H}[/tex]

[tex]\cos 30^\circ = \dfrac{B}{8}[/tex]

[tex]B = \dfrac{8\times \sqrt{3}}{2}[/tex]

[tex]B = 4\sqrt 3[/tex]

Area of sector = [tex]\dfrac{\theta}{360^\circ}\times \pi r^2[/tex]

Area of sector =  [tex]\dfrac{30^\circ}{360^\circ}\times \pi \times 8^2[/tex]

                        = 16.75 cm^2

Area of triangle = [tex]\dfrac{1}{2} \times 4\sqrt 3 \times 4[/tex]

                          = 13.85 cm^2

Area of shaded region = 16.75 - 13.85

                                      = [tex]2.9 cm^2[/tex]

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