Hiány barát Emberi faj a pi r 2 Ürítsd ki a szemetest krizantém Érvényesül
Neil deGrasse Tyson on Twitter: "For Algebra Pizza Geeks on #PiDay... The volume of a cylinder is V = pi r^2 h Think of a Pizza as a very short, wide cylinder,
Area of a circle - Wikipedia
How did we come to know that the area of a circle is pi r^2? - Quora