Answer:
[tex]x^2 + y^2 =18[/tex]
Step-by-step explanation:
The standard equation of a circumference has the following formula.
[tex](x-h) ^ 2 + (y-k) ^ 2 = r ^ 2[/tex]
Where the point (h, k) is the center of the circle and r is the radius.
If in this case we know that the circle has center at point (0,0), then its equation will have the following form
[tex]x ^ 2 + y ^ 2 = r ^ 2[/tex]
The radius of the circumference will be the distance from the center of the circumference to the point where the circumference is tangent to the line [tex]Ax + Bx + C = 0[/tex]
The radio is:
[tex]r=\frac{|Ah + Bk +C|}{\sqrt{A^2+B^2}}[/tex]
In this case, the line is
[tex]x + y = 6[/tex]
And the center of the circumference is (0, 0)
So
[tex]A = 1\\B = 1\\C = -6\\h = 0\\k = 0[/tex]
The radio is:
[tex]r=\frac{|1*0 + 1*0 -6|}{\sqrt{1^2+1^2}}\\\\r=\frac{|-6|}{\sqrt{1^2+1^2}}\\\\r=\frac{6}{\sqrt{2}}[/tex]
Finally the equation of the circumference is:
[tex]x^2 + y^2 =(\frac{6}{\sqrt{2}})^2\\\\x^2 + y^2 =18[/tex]
