66. Exemplar exercise problems XXXXII

The central angles of two sectors of circles of radii \(7 \ cm\) and \(21 \ cm\) are respectively \(120^\circ\) and \(40^\circ\). Find the areas of the two sectors as well as the lengths of the corresponding arcs. What do you observe?

 

When radius \(7 \ cm\)  and central angle \(120^\circ\):

 

Area of sector \(=\) \(cm^2\)

 

Length of the arc \(=\) \(cm^2\)