## Wednesday, December 12, 2012

### December 11, 2012

Today we learned the formulas for finding the surface areas (S.A) of a:

1. Cube
2. Rectangular Prism
3. Pyramid
4. Cylinder
In order to find the surface area of a cube, use this formula:

S.A = 6 s²
(Where "s" is the measure of 1 edge.)
That means that to find the surface area of a cube, find the area of one face of the cube first. Then square that number (multiply it by itself), and multiply it by 6 and you have your final answer.

To find the surface area of a rectangular prism, do this:

S.A = 2B + Ph
(Where "B" is the area of the base formed by multiplying its length by its width. "P" is the perimeter of the base multiplied by "h", the height of the prism.

or.......

S.A = 2 (lw + lh + wh)
(Where "l" stands for length, "h" is height and "w" is width.)

Finding the surface area of a pyramid... :

S.A = B + ½ Ps
(Where "B" is the area of the base. "P" is the perimeter, "s" is the slant height.)

The surface area formula for a cylinder:

S.A = π r ² + 2 π rh

or......

S.A = 2 π r (r + h)
(Where "r" is radius and "h" is height.)

And lastly, for finding the surface area of an isosceles triangular prism:

S.A = 2 (bh/2) + 2 b2 h2 + B)
(Where "b" is the base of the triangle, "h" is the height of the triangle, "b2" the base of the rectangle, "h2" is the slant height of the rectangle, and "B" represents the base of the figure found by multiplying "b" by "b2"

(sorry I couldn't upload any pictures!)