The power of point P with respect to circle c is $-R^2+d^2$ where d is the distance from point P to the center of c, and R is the radius of c.

The command with(geometry,powerpc) allows the use of the abbreviated form of this command.

$\mathrm{with}\left(\mathrm{geometry}\right)\:$

$\mathrm{\_EnvHorizontalName}≔a\:$$\mathrm{\_EnvVerticalName}≔b\:$

$\mathrm{point}\left(A\,3\,0\right),\mathrm{point}\left(B\,\frac{6}{7}\,2\right)\:$

$\mathrm{circle}\left(c\,a^2+b^2=1\right)\:$

$\mathrm{powerpc}\left(A\,c\right)$

$8$

$\mathrm{powerpc}\left(B\,c\right)$

$\frac{183}{49}$