waecmaths question:
In the diagram O is the centre of the circle of radius 18cm . If $\angle ZXY=70{}^\circ $, Calculate the length of arc ZY [Take $\pi =\tfrac{22}{7}$]
Option A:
11 cm
Option B:
22 cm
Option C:
44 cm
Option D:
80 cm
waecmaths solution:
$\begin{align} & \angle ZOY=2\times \angle ZXY\text{ } \\ & \text{ }\!\!\{\!\!\text{ }\angle \text{ at centre}=2\times \angle \text{ subtended on the circum}\text{. }\!\!\}\!\!\text{ } \\ & \angle ZOY=2\times 70{}^\circ =140{}^\circ \\ & \text{Length of arc}=\frac{\theta }{360{}^\circ }\times 2\pi r \\ & l=\frac{140{}^\circ }{360{}^\circ }\times 2\times \frac{22}{7}\times 18cm \\ & l=44cm \\\end{align}$
maths year:
maths topics: