Question
In figure, points G, D, E, F are concyclic points of a circle with centre C
$\angle E C F=70^{\circ}, m(\operatorname{arc} D G F)=200^{\circ}$
Find $m$ (arc DEF) by completing activity.
$ m(\operatorname{arc} E F)=\angle E C F \quad \ldots \ldots[\text { Definition of measure of } \operatorname{arc}]$
$\therefore m(\operatorname{arc} E F)=\square$
$B u t ; m(\operatorname{arc} D E)+m(\operatorname{arc} E F)+m(\operatorname{arc} D G F)=\square \quad \ldots \ldots[\text { Measure of a complete circle] }$
$\therefore m(\operatorname{arc} D E)=\square$
$\therefore m(\operatorname{arc} D E F)=m(\operatorname{arc} D E)+m(\operatorname{arc} E F)$
$\therefore m(\operatorname{arc} D E F)=\text { square } $
$\angle E C F=70^{\circ}, m(\operatorname{arc} D G F)=200^{\circ}$
Find $m$ (arc DEF) by completing activity.
$ m(\operatorname{arc} E F)=\angle E C F \quad \ldots \ldots[\text { Definition of measure of } \operatorname{arc}]$
$\therefore m(\operatorname{arc} E F)=\square$
$B u t ; m(\operatorname{arc} D E)+m(\operatorname{arc} E F)+m(\operatorname{arc} D G F)=\square \quad \ldots \ldots[\text { Measure of a complete circle] }$
$\therefore m(\operatorname{arc} D E)=\square$
$\therefore m(\operatorname{arc} D E F)=m(\operatorname{arc} D E)+m(\operatorname{arc} E F)$
$\therefore m(\operatorname{arc} D E F)=\text { square } $
