The standard equation of a circle is given by :
[tex] (x-h)^{2} + (y-k)^{2} =r^{2} [/tex]
where (h,k) is the center and r is the radius of circle.
Now in the question we are given that the center is at origin.
So coordinate of center becomes (h,k) =(0,0)
radius is r.
So plugging these values in the standard equation, we get,
[tex] (x-0)^{2} + (y-0)^{2} =r^{2} [/tex]
Simplifying,
[tex] (x)^{2} + (y)^{2} =r^{2} [/tex]
Answer is option first:
x² + y² =r²
