07/05/09

Hey!
Today in class we went over the Home work, (it was page 588 #23, 24, 25) although they were only a few problems they were complicated. To simplfy things it is much easier if you seperate them into different parts, number 23 for example can be the two bases (the bases being the L shapes, since they are parallel and congruent) two equal rectangles, the back rectangle and the two smaller rectangles. And after you have added up all the seperate areas you will have 120 units squared. The second problem is very similar, find the area of the pentagon using the idea of apothem times perimeter divided by two, and then multiply it by two since they are two hexagons. Then find the area of the rectangle and multiply by six (the number of rectangles). The last one was the most complicated, you have to pay attention to realize that the top edge is actually smaller than the middle edge.
Now, in class we began with some definitions, Ms. Saatkamp stressed the fact that many times the problem will actually give us a description of the solid rather than a diagram so it is important to understand the definitions. There are basically 3 names when naming prisms, such as Right Hexagonal Prism. The first name may be either right or oblique, the second being the shape of the bases such as hexagonal or triangular, the third name is prism, just to give it an ending :P
Then Ms. Saatkamp gave us some shapes to cut up, which was pretty fun. One of the shapes we cut up was an open Right Pentagonal Prism. Which by looking at opened looks like 5 rectangles and 2 pentagons. I'm sorry i'm having a lot of trouble getting pictures on here. Anyways, by looking at it you can see that the perimeter of a penatgon is = to the side the big rectangle(if you join all 5 rectangles it forms a big one).
To find the total surface area you use the following formula:
T = L + 2B
T being total area. L being Lateral area (which you can find by multiplying perimeter and height) 2B being twice the area of the base.
Homework is pg 596 #15-25 +32 and 33
bjos