9.2.notebook
May 03, 2011
9-2 Developing Formulas for Circles
Circle - The locus of all points in a plane that are a fixed distance
from a point (center).
A circle is named by it's center. Use the symbol,
A
CD is a diameter
AB is a radius
The number π...
First of all, π is an irrational number which means that it's a never
ending, never-repeating decimal.
It can be approximated by 3.14159... or 22/7
Current world record holder for memorizing digits of pi is Chao Lu
who memorized 67,890 digits
The current record for finding the most digits of pi is 51 billion
decimal places
http://www.geom.uiuc.edu/~huberty/math5337/groupe/digits.html
9.2.notebook
May 03, 2011
Chances of Finding
Why can/can't I find my number in Pi? If we view Pi as a big, random string of numbers (which is close enough for our purposes), then we can figure out the odds of finding any string in the first 100 million digits of Pi:
Happily, if you include the zeros, birthdays are 8 digits long ­­ so you have a 63% chance of finding your birthday in the first 100 million digits of pi. Now that we're up to 200 million, the odds are up to 86%.
http://www.angio.net/pi/piquery
Pi was discovered because it is the ratio of a circle's circumference to
it's diameter.
Circumference - the distance around a circle
To find a circle's circumference, C = 2πr or C = πd
Ex.) If the radius of a circle is 6, what's it's circumference?
9.2.notebook
Area of a circle
So far, we've been able to figure out all of our area formulas by
comparing them to a parallelogram.
Can we do this with a circle also?
Area of a circle is A = πr2
May 03, 2011
9.2.notebook
May 03, 2011
9.2.notebook
May 03, 2011
HW: p. 603 #10 - 13, 34 - 37