check the picture below. so the circle looks like so, and those points, are pretty much endpoints for the radius "r", thus
[tex]\bf \textit{distance between 2 points}\\ \quad \\
\begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
% (a,b)
&({{ -3}}\quad ,&{{ 3}})\quad
% (c,d)
&({{ 1}}\quad ,&{{ 6}})
\end{array}\qquad
% distance value
d = \sqrt{({{ x_2}}-{{ x_1}})^2 + ({{ y_2}}-{{ y_1}})^2}
\\\\\\
r=\sqrt{[1-(-3)]^2+[6-3]^2}\implies r=\sqrt{(1+3)^2+(6-3)^2}
\\\\\\
r=\sqrt{4^2+3^2}\implies r=\sqrt{25}\implies \boxed{r=5}\\\\
-------------------------------\\\\
\textit{area of a circle}\\\\
A=\pi r^2\qquad r=5\implies \boxed{A=25\pi }[/tex]
