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A circle has a center of [tex]$(-3, -4)$[/tex] and the endpoints of a diameter of the circle are [tex]$(0, 2)$[/tex] and [tex]$(-6, -10)$[/tex]. What is the equation of the circle?

[tex]\[
(x - \qquad )^2 + (y - \qquad )^2 = \qquad
\][/tex]


Sagot :

To find the equation of a circle given the center and the endpoints of a diameter, follow these steps:

1. Identify the center of the circle:
The center of the circle is [tex]\((-3, -4)\)[/tex].

2. Calculate the radius of the circle:
Use the distance formula to find the length of the diameter first. The formula for the distance between two points [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] is:
[tex]\[ d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \][/tex]
The given endpoints of the diameter are [tex]\((0, 2)\)[/tex] and [tex]\((-6, -10)\)[/tex]. Plugging in these values:
[tex]\[ d = \sqrt{(0 - (-6))^2 + (2 - (-10))^2} = \sqrt{6^2 + 12^2} = \sqrt{36 + 144} = \sqrt{180} \][/tex]
The diameter is [tex]\(\sqrt{180}\)[/tex], and the radius [tex]\(r\)[/tex] is half of the diameter:
[tex]\[ r = \frac{\sqrt{180}}{2} = \sqrt{45} \approx 6.708203932499369 \][/tex]

3. Formulate the equation of the circle:
The general form of the equation of a circle is [tex]\((x - h)^2 + (y - k)^2 = r^2\)[/tex], where [tex]\((h, k)\)[/tex] is the center and [tex]\(r\)[/tex] is the radius.
Here, the center [tex]\((h, k) = (-3, -4)\)[/tex], and [tex]\(r^2 = (\sqrt{45})^2 = 45\)[/tex].

Thus, the equation of the circle is:
[tex]\[ (x - (-3))^2 + (y - (-4))^2 = 45 \][/tex]
Simplifying:
[tex]\[ (x + 3)^2 + (y + 4)^2 = 45 \][/tex]

So filling in the provided boxes:
[tex]\[ \boxed{ -3 } \;\;\boxed{ -4 }\;\;\boxed{ 45 } \][/tex]

The final equation is:
[tex]\[ (x + 3)^2 + (y + 4)^2 = 45 \][/tex]