A circle is drawn on a coordinate plane with the center point at ( -1,3) and a radius of 5. Derive the equation of the circle in standard form, using the given information and the Pythagorean theorem.

(X+1)^2 +(y-3)^2=25
(X-1)^2 +(y-3)^2=25
(X-3)^2+(y-1)^2=25
(X+3)^2+(y-1)^2=25

1 answer

To derive the equation of a circle in standard form, we use the formula:

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

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

Given:

  • Center \((h, k) = (-1, 3)\)
  • Radius \(r = 5\)

We can substitute these values into the formula:

  1. Substitute \(h\) and \(k\): \[ (x - (-1))^2 + (y - 3)^2 = 5^2 \]

  2. Simplify: \[ (x + 1)^2 + (y - 3)^2 = 25 \]

Thus, the equation of the circle in standard form is:

\[ (x + 1)^2 + (y - 3)^2 = 25 \]

From the options you provided, the correct equation is:

\[ (X + 1)^2 + (y - 3)^2 = 25 \]