Scribe Post - Madison - Ch 6

Today in class we started by taking Daily Quiz #19 which involved using the equations for circumference and diameter. Shakespeare put those on his scribe post yesterday for anyone who needs a refresher.

We then went over some problems in class from the homework problems from 2 nights ago. One of them, 2c looked like this:

• A circle has a circumference of exactly 7pi/2 feet. What is the exact length of the diameter?
• Start by stating what you know, C(circumference) = 7pi/2 and the formula for diameter D=c/pi
• We now have a systems of equations. So plug in! D= 7pi/2|pi/1 (7pi/2 is over pi/1 making it a fraction)
• Because we have two fractions on top of each other, we multiply by the reciprocal of the bottom fraction, 7pi/2 x 1/pi This causes the two pi symbols to cancel out, creating D= 7/2 which equals 3.5. So the exact length of the diameter of the circle is 3.5 feet.
  

I'm sorry if that looks a little confusing. All the 'pi' are the pi symbol and all the / and | marks are fraction bars!

We then went over how to find the area of a circle.

The formula to find area is (where r is the radius of the circle.)


The area here is given in terms of the radius, but because we know that D=2r, IF it is given in terms of the DIAMETER, we'll know how to do it!

Jojo told us that area has to do with space that is measured in square units and circumference has to do with length and distance.


Some helpful links that can explain further about finding the area of a circle. A little dry, but hey, they work.
http://www.mathgoodies.com/lessons/vol2/circle_area.html

http://www.youtube.com/watch?v=eBAsK9jB91I (She's a little....robot-y but it really explains what we went over!!)

http://www.youtube.com/watch?v=Q081LTbFtMo&feature=PlayList&p=0A3DF1D5B4A25D75&playnext=1&playnext_from=PL&index=4 (this one you can pause on the steps)

Everyone remember to post their circle picture on Flickr!!!! Remember that it can take a couple of days to show up....!

Next scribe is Camille