Angle between the circles.

For two circles, $x^2 + y^2 + 2g_1x + 2f_1y + c_1 = 0$ and $x^2 + y^2 + 2g_2x + 2f_2y + c_2 = 0$ , to be orthogonal, the following condition must be satisfied.

$2g_1g_2 + 2f_1f_2 = c_1 + c_2$

On applying the above condition, we get $a^2 + b^2 = 0$ .

this implies $a=b=0$

But these values of $a$ and $b$ make the circles concentric. Hence there is no actual intersection of the circles possible which may make them orthogonal.