Question

What is the radius of the circle whose equation is x2 + y2 = 8?

Answer 1

If that is x^2+y^2=8
then the radius is 2$\sqrt{2}$

Answer 2

Answer:

The radius of the circle whose equation is $x^{2}+y^{2}=8$ is $2\sqrt{2}$

Step-by-step explanation:

The equation of a circle centered at the origin $(0,0)$ and radius $R$ is :

$x^{2}+y^{2}=R^{2}$ (I)

Where ''$R$'' is a real number.

For the equation given, we know that

$R^{2}=8$ ⇒

$R=\sqrt{8}$

$R=\sqrt{(2).(4)}$

$R=2\sqrt{2}$

We found out that the radius of the circle is $R=2\sqrt{2}$

For another circle, for example centered at the point $(a,b)$ and radius $R$ the equation is :

$(x-a)^{2}+(y-b)^{2}=R^{2}$  (II)

Notice that if we replace the point $(a,b)$ by $(0,0)$ ⇒

$(x-0)^{2}+(y-0)^{2}=R^{2}$ ⇒

$x^{2}+y^{2}=R^{2}$

We obtain the equation (I).