Selasa, 04 Desember 2012

Surface Area of Cylinders and Spheres

Surface Area of Cylinders

A cylinder has a total of three surfaces: a top, bottom, and middle. The top and bottom, which are circles, are easy to visualize.
• the area of the top (πr2) +
• the area of the bottom (πr2) +
• the area of the side (2πrh).
Therefore without the top or bottom (lateral area), the surface area is:
A = 2πrh.
With the top and bottom, the surface area is:
A = 2πr2 + 2πrh = 2πr(r + h).

Surface Area of Spheres
SA   =     4 • π • r²
=     π • d²
This formula was first derived by Archimedes.