Answer
See the graph below:
Work Step by Step
We know that for a circle that has center $\left( h,k \right)$ and radius $r$ , the general equation of the circle is ${{\left( x-h \right)}^{2}}+{{\left( y-k \right)}^{2}}={{r}^{2}}$.
The equation ${{x}^{2}}+{{y}^{2}}=4$ can be rewritten as ${{\left( x-0 \right)}^{2}}+{{\left( y-0 \right)}^{2}}={{2}^{2}}$. So, the center of the circle $\left( h,k \right)=\left( 0,0 \right)$ and radius $r=2$.
In order to plot this circle on the rectangular coordinate system, take $\left( 0,0 \right)$ as a center and draw a circle with radius $r=2$.
