In the diagram above, \(\alpha\) = 2m^o (angle at centre = 2 x angle at circumference)

\(\alpha\) + 10m^o = 360^o (angle at circumference)

\(\alpha\) + 10m^o = 360^o(angles round a point)

2m^o + 10m^o = 360^o

12m^o = 360^o

m^o = \(\frac{360^o}{12}\)

= 30^o