JAMB - Mathematics (2016 - No. 28)
An arc subtends an angle of 30º at the centre of a circle radius 12cm. Calculate the length of the arc.
6\(\pi\)cm
2\(\pi\)cm
3\(\pi\)cm
9\(\pi\)cm
Explication
Length or arc = \(\frac{\theta}{360}\) x 2\(\pi\)r
= \(\frac{30}{360}\) x 2 x \(\frac{22}{7}\) x 12
= \(\frac{1}{12}\) x 2 x \(\pi\) x 12 = 2\(\pi\)cm
= \(\frac{30}{360}\) x 2 x \(\frac{22}{7}\) x 12
= \(\frac{1}{12}\) x 2 x \(\pi\) x 12 = 2\(\pi\)cm