Before the video I knew about the formulas for finding the circumference, radius, and diameter of a circle. Also, I knew about the different parts of a circle (diameter, chord, and radius). Lastly, I knew about how to find the radius and diameter and this is all I knew before the video.
After the video I learned about congruent circles and concentric circles (coplanar circles). For two circles to be congruent, the two circles have to have congruent radii. For two circles to be concentric circles (coplanar circles), they have to have the same center. I also learned about finding measures in intersecting circles. Like one of the questions in the video had you find the length of XY. You where given the diameter of circle X and the diameter of circle Y, which is twenty-two and sixteen. Lastly, you were given the length of WZ, which is five. First, you have to find the radius of the two circles. To find the radius you can use the diameter formula, which is diameter = 2 * radius. Let’s find the radius of circle X. Since you have the diameter of circle X. You plug it in the formula and get 22=2r. Then, you divide 22/2 and get your radius to equal 11. You do the same thing to circle Y and get the radius to equal 8. So, you add 6+5+3 and get 14. So, 14 is the length of XY. The last thing I learned was about finding the exact circumference. All you have to do is find the circumference, but instead of multiplying it by π, you just leave it. For example, if the radius is 6, the formula would look like this: C=2π(6). Then, you multiply 2 times 6 and get 12. So, your exact circumference would be 12π.
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Questions:
1.) Can someone explain how to get the answer to the question on slide 11? I don’t get it.
2.) Can someone explain how to get the answer to the question on slide 15? I don’t get it.
Well for the first question you have to take what is given to you then you have to find all the small pieces of it. So you have to find AB, BC, and then you can find AC. So then you can take 9=2r and then solve for r so r=4.5 in for AB, then you take 4.5=BC+2 and then solve for BC so BC=2.5 and finally for AC you take AC=AB+BC so AC=4.5+2.5 and AC=7in. For your second question you have to find x of the triangle because if you find x then you can plug that number into the circumference equation so you have what the circumference equals. So to do that you can take the Pythagorean theorem of the triangle so you will have x^2+x^2=(3 square root of 2)^2 so then doing so you just solve and you will end up getting x to equal 3 and plug it into the circumference equation so circumference will end up equaling 6pie units.
ReplyDeleteHey Amy very nice job of explaining this section. Very good information has been provided. I am going to do your problem number one. You know D's diameter is 4 so for inside the big circle you would subtract 2. The you know that A's diameter is 18 but cut it in half into 9. Take 9 and minus it by 2 and you would get 7. So your answer to the question would be C.
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