Explanation
Let the equation of the general form of the required circle be
$$x^2+y^2+2gx+2fy+c=0$$................(1)
According to the problem, the above equation of the circle passes through the points $$(0, 6), (0, 0)$$ and $$(8, 0)$$. Therefore,
$$36 + 12f + c = 0$$ ………. (2)
$$ c = 0$$ ……………. (3)
$$64 + 16g + c = 0$$ ……………. (4)
Putting $$c = 0$$ in (2), we obtain $$f = -3$$. Similarly put $$c = 0$$ in (4), we obtain $$g=-4$$
Substituting the values of $$g, f$$ and $$c$$ in (1), we obtain the equation of the required circle as:
$$x^2+y^2+2(-4)x+2(-2)y+0=0$$ that is
$$x^2+y^2-8x-4y+0=0$$ can be rewritten as
$$x^2+y^2-8x-4y+16+9=0+16+9$$
$$(x-4)^2+(y-3)^2=25$$
Therefore, the equation of circle is $$(x-4)^2+(y-3)^2=25$$.
Let $$s: x^2 + y^2 + 2gx + 2fy +c = 0$$ be the equation of the circle
$$S(0,2) = 0$$
$$\implies 4 + 4f + c =0 -eq.1$$
Intercept on x-axis is given by
$$2\sqrt{g^2 - c} = 4$$
$$g^2 – c = 4 -eq.2$$
Since x = 0 is a tangent
Radius = perpendicular distance from the center to tangent
$$\sqrt {g^2 + f^2 - c} = \dfrac{|-g|}{\sqrt{1 + 0}$$
$$ g^2 + f^2 - c = g^2 $$
$$f^2 = c$$
Substituting in eq.1
$$4 + 4f + f^2 =0 \implies (f+2)^2 = 0 \implies f = -2 $$
$$\implies c = 4$$
From eq.2
$$g^2 – 4 = 4$$
$$g = \pm 2 \sqrt{2}$$
Equation of circle is
$$x^2 +y^2 \pm 4\sqrt 2 x – 4y + 4 = 0$$
$$\implies x^2 +y^2 – 4(\sqrt 2 x + y) + 4 = 0$$
The circumference of the circle is given as $$10\pi $$.
$$C = 2\pi r$$
$$10\pi = 2\pi r$$
$$r = \frac{{10\pi }}{{2\pi }}$$
$$r = 5$$
The general form of the equation is,
$${\left( {x - h} \right)^2} + {\left( {y - k} \right)^2} = {r^2}$$
The center of the circle is given as $$\left( {h,k} \right) = \left( {2, - 3} \right)$$
$${\left( {x - 2} \right)^2} + {\left( {y - \left( { - 3} \right)} \right)^2} = {\left( 5 \right)^2}$$
$${\left( {x - 2} \right)^2} + {\left( {y + 3} \right)^2} = 25$$
$${x^2} + 4 - 4x + {y^2} + 9 + 6y = 25$$
$${x^2} + {y^2} - 4x + 6y + 13 = 25$$
$${x^2} + {y^2} - 4x + 6y - 25 + 13 = 0$$
$${x^2} + {y^2} - 4x + 6y - 12 = 0$$
Therefore, the equation of the circle is,
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