JAMB - Mathematics (2003 - No. 36)
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.
11cm
22cm
44cm
66cm
설명
θ = 30 x 2(∠ at center twice ∠ at circumference)
∴ θ = 60°
Length of arc = \(\frac{\theta}{360}\times 2\pi r\)
= \(\frac{60}{360}\times 2 \times \frac{22}{7}\times \frac{21}{1}\)
= 22cm