Class of February 3rd - - 9B

We began our class today by correcting yesterday’s homework, which was about PROPORTIONS. Exercise # 33 was one of the exercises people had most problems with, along with #44. Here are the answers:

#33
#44 a) 10 and 7.75 (approximately) b) 63.6

(The figures above show some of the possible formulas one can use to get to the answers.)

After that, we began a new topic: SIMILAR POLYGONS. Similar Polygons are shaped figures that have the same angles but have different sides; their corresponding angles are congruent, their corresponding sides are proportional and their corresponding ratios are equal. For example:

and

As we saw in exercise #1, when a comparison of the perimeters and areas of similar polygons is made, while the area from one polygon to the other is x, the perimeter from one polygon to the other will be x². For example, in exercise #1, the area from one polygon increased three times, while the perimeter increased 9 times, which is 3².

A reminder: Circles, Squares, Equilateral Triangles and any other Regular Polygons will ALWAYS be similar.

So, the homework for tomorrow is Page 351, # 15 – 32 all!