Odpowiedź :
[tex]\frac{\alpha}{360^o}\pi r^2=18\pi\ \ \ |:\pi\\\\\frac{\alpha}{360^o} \cdot 30^2=18\\\\\frac{\alpha}{360^o} \cdot 900=18\ \ \ |:\frac{900}{360}\\\\\alpha=7,2^o[/tex]
[tex]\frac{\alpha}{360^o}\pi r^2=18\pi\ \ \ |:\pi\\\\\frac{\alpha}{360^o} \cdot 30^2=18\\\\\frac{\alpha}{360^o} \cdot 900=18\ \ \ |:\frac{900}{360}\\\\\alpha=7,2^o[/tex]