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Question 193915: PLEASE HELP ME WITH THIS!
Use the given information to write an equation of the circle.
16. radius 3, center (2, 4)
17. area 12.57, center (1, -2)
18. center (5, -1), circumference 5p
19. center (0, 0), passing through (2, 0)
Answer by solver91311(24713)   (Show Source):
You can put this solution on YOUR website!
Writing the equation of a circle is a simple matter of plugging in values once you have the coordinates of the center and the radius.
A circle with center at ) and radius 
is:
^2 + (y - k)^2 = r^2)
So for your problem 16, just stick in the values:
radius 3, center (2, 4)
^2 + (y - 4)^2 = 9)
Then, depending on the form your instructor or your textbook wants, you might want to expand the binomials:
And collect terms:
17. Works the same way, except that here you are given the area instead of the radius, but we know that the area equals  , so the radius squared is simply the area divided by  .
18. This time you have the circumference instead of the radius, but we know that  so divide the circumference by  and square the result to get 
19. The distance between the center of a circle and any point on the circle is the radius. When you have two points and want to know the distance between them, use the distance formula:
^2 + (y_1 - y_2)^2})
where ) and ) are the coordinates of the given points.
But you can save a couple of calculation steps if you realize that what you really need for the equation of your circle is which is the same as  , so:
^2 + (y_1 - y_2)^2)
John
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