Answer
63 (a). 44.68 square unit
63 (b). 25 square unit
Work Step by Step
Given-
Central angle of the sector. $\theta$ = $80^{\circ}$
or, $\theta$ = $80\times\frac{\pi}{180}$ = $\frac{4\pi}{9}$ rad
radius, r = 8 unit
A = ?
We know that area 'A' of a circular sector with central angle $\theta$ rad and radius 'r' is given by-
A = $\frac{1}{2} r^{2} \theta$
= $\frac{1}{2}\times 8^{2}\times \frac{4\pi}{9}$
=$\frac{64\times2\pi}{9}$ = $\frac{128\pi}{9}$ square unit
= 44.68 square unit
63 (b).
Given-
Central angle of the sector. $\theta$ = 0.5 rad
radius, r = 10 unit
A = ?
We know that area 'A' of a circular sector with central angle $\theta$ rad and radius 'r' is given by-
A = $\frac{1}{2} r^{2} \theta$
= $\frac{1}{2}\times 10^{2}\times 0.5$
=$\frac{100\times0.5}{2}$ = $\frac{50}{2}$ square unit
= 25 square unit
