An arc of a circle subtends an angle of 30∘ ∘ on the circumference of a circle of radius 21cm. Find the length of the arc.

An arc of a circle subtends an angle of 30${}^{\circ }$ on the circumference of a circle of radius 21cm. Find the length of the arc.

Answer Details

θ = 30 x 2(∠ at center twice ∠ at θ)
∴ θ = 60${}^{\circ }$
Length of arc =$\frac{\theta }{360}\times 2\pi r=\frac{60}{360}\times 2\times \frac{22}{7}\times \frac{21}{1}=22cm$