[tex]\it a)\ \ MO=30dm=3m\\ \\ ON\perp MN \Rightarrow \Delta ONM-dreptunghic,\ m(\widehat{N})=90^o,\ \stackrel{T.P.}{\Longrightarrow}\ ON^2=MO^2-MN^2\\ \\ ON^2=3^2-(2\sqrt2)^2=9-8=1 \Rightarrow ON=1m\ (raza\ cercului).\\ \\ \mathcal{A}_{piscin\breve a} =\pi R^2=\pi\cdot1^2=\pi\approx3,14\ m^2[/tex]
[tex]\it b)\ \ Fie\ NF\perp MO \Rightarrow NF=\dfrac{ON\cdot MN}{MO}=\dfrac{1\cdot2\sqrt2}{3}\approx\dfrac{2\cdot1,41}{3} \Rightarrow \\ \\ \Rightarrow NF\approx0,94m;\ \ \ AB=2R=2\ m\\ \\ \mathcal{A}_{ANB}=\dfrac{AB\cdot NF}{2} \approx\dfrac{2\cdot0,94}{2} =0,94\ m^2<0,95\ m^2[/tex]
