Question:
In a circle of radius 10 cm, an arc subtends an angle of 108° at the centre. what is the area of the sector in terms of π?
Solution:
We have given the radius of the circle and angle subtended at the centre of the circle.
$r=10 \mathrm{~cm}$
$\theta=108^{\circ}$
Now we will find the area of the sector.
Area of the sector $=\frac{\theta}{360} \times \pi r^{2}$
Substituting the values we get,
Area of the sector $=\frac{108}{360} \times \pi \times 10^{2}$....(1)
Now we will simplify the equation (1) as below,
Area of the sector $=\frac{3}{10} \times \pi \times 100$
Area of the sector $=3 \times \pi \times 10$
$\Rightarrow$ Area of the sector $=30 \pi$
Therefore, area of the sector is $30 \pi \mathrm{cm}^{2}$.