[Risolto] Aiuto es 66

66)

Area del segmento circolare:

$A= \dfrac{r^2·\pi·\alpha}{360°}-\dfrac{r^2·sen(\alpha)}{2}$

$A= \dfrac{4^2·\pi·90°}{360°}-\dfrac{4^2·sen(90°)}{2}$

$A= \dfrac{16·\pi·\cancel{90°}^1}{\cancel{360°}_4}-\dfrac{16·1}{2}$

$A= \dfrac{16·\pi·1}{4}-\dfrac{\cancel{16}^8}{\cancel2_1}$

$A= \dfrac{\cancel{16}^4·\pi·1}{\cancel4_1}-\dfrac{8}{1}$

$A= 4\pi-8$

$A\approx{4,566}\,cm^2.$