In the standard [tex]$(x, y)$[/tex] coordinate plane, a circle with its center at [tex]$(8,5)$[/tex] and a radius of 9 coordinate units has which of the following equations?

A. [tex]$(x-8)^2+(y-5)^2=81$[/tex]

B. [tex]$(x-8)^2+(y-5)^2=9$[/tex]

C. [tex]$(x+8)^2+(y+5)^2=81$[/tex]

D. [tex]$(x+8)^2+(y+5)^2=9$[/tex]

E. [tex]$(x+5)^2+(y+8)^2=81$[/tex]



Answer :

To find the equation of a circle in the standard [tex]\((x, y)\)[/tex] coordinate plane, we use the general formula for the equation of a circle, which is:

[tex]\[ (x - h)^2 + (y - k)^2 = r^2 \][/tex]

where [tex]\((h, k)\)[/tex] is the center of the circle, and [tex]\(r\)[/tex] is the radius.

Given:
- The center of the circle is [tex]\((8,5)\)[/tex].
- The radius of the circle is 9 units.

We substitute these values into the equation of the circle:

1. Substituting [tex]\(h = 8\)[/tex], [tex]\(k = 5\)[/tex], and [tex]\(r = 9\)[/tex] into the formula, we get:
[tex]\[ (x - 8)^2 + (y - 5)^2 = 9^2 \][/tex]

2. Next, we calculate [tex]\(9^2\)[/tex]:
[tex]\[ 9^2 = 81 \][/tex]

3. Therefore, the equation of the circle is:
[tex]\[ (x - 8)^2 + (y - 5)^2 = 81 \][/tex]

From the provided choices, the correct answer is:

F. [tex]\((x - 8)^2 + (y - 5)^2 = 81\)[/tex]