Odpowiedź:
[tex]r=46\frac{2}{3}[/tex]
Szczegółowe wyjaśnienie:
[tex]P_W=\frac{a\lpha}{360^\circ}*\pi r^2\qquad l=\frac{a\lpha}{360^\circ}*2\pi r\\\frac{a\lpha}{360^\circ}*\pi r^2=70\pi\qquad \frac{a\lpha}{360^\circ}*2\pi r=3\pi\ |:2\\\underbrace{\frac{a\lpha}{360^\circ}*\pi r}_{=\frac{3}{2}\pi}*r=70\pi\qquad \frac{a\lpha}{360^\circ}*\pi r=\frac{3}{2}\pi\\\frac{3}{2}\pi*r=70\pi\ |:\frac{3}{2}\pi\\r=70*\frac{2}{3}\\r=\frac{140}{3}\\r=46\frac{2}{3}[/tex]
