Review: The Circumference of a circle is ______________________________.

We can compare it to the ___________________of a polygon.

Let's look at a circle:

We would call this circle circle A, since A is the circle's center.

In this circle we can draw many radii (which we discussed in chapter 10!) We will draw 1 radius.

The radius we have drawn is radius AB.

The formula for the Circumference of a circle is C = or _____.

Assignment #6: Draw the following circles and find the missing measurements in terms of pi.

1.) Find the Circumference of a circle with a radius of 4 meters.

2.) Find the Circumference of a circle with a diameter of 6 meters.

3.) Find the radius of a circle that has a Circumference of 12 cm.

4.) Find the diameter of the previous problem.

5.) Create an original problem about Circumference. Pose it as a word problem in a real life situation.

Arc GB is the shortest DISTANCE from G to B on the above circle. Notice that we are not measuring in degrees. We want to find how far it is from G to B.

If we wanted to find the greater distance from G to B, we would place another point on the circle to guide us the other way.

Assignment #7: Thins about how you would find the circumference for a portion of a circle. Be prepared to discuss your ideas with the class.

How do we find the length of an arc?

1.) It is part of the circumference, so let's find that first!here are the measurements that we are given:

Therefore the Circumference is C =

2.) Since the arc takes up 80 degrees of the circle, we multiply 80 times the circumference which gives us:

3.) Is that our solution? Does it make sense? Recall, we said that the TOTAL distance around the circle is 4pi, but the length of the arc is 320pi. So, if this circle was a track, to run partway around is a greater distance than running all the way around! NO THAT DOES NOT MAKE SENSE!!!!!

4.) We forgot that we need to divide by the total degrees of a circle or 360.

5.) Therefore the arc length is 320pi/360=

1.) Construct a circle with an arc measure of 35 degrees and diameter of 3 cm. Find the measure of the small arc length.

2.) Construct a circle with a central angle measuring 83 degrees and a radius of 2 cm. Find the measure of the samll arc length.

3.) Construct a circle with your own measurements and find the arc length. Be prepared to present your problem to the class

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