Firstly we will represent the geometric objects in a more convenient formulation.
So
C_1->y^2+x^2-4x-6y+9=0C1→y2+x2−4x−6y+9=0 for
C_1->(x-x_1)^2+(y-y_1)^2=r_1^2C1→(x−x1)2+(y−y1)2=r21
C_2->y^2+x^2+10x-16y+85=0C2→y2+x2+10x−16y+85=0 for
C_2->(x-x_2)^2+(y-y_2)^2=r_2^2C2→(x−x2)2+(y−y2)2=r22
L_1->x+2y+15=0L1→x+2y+15=0
L_1->p = p_3+lambda_3 vec v_3L1→p=p3+λ3→v3
After reduction, we have
p_1=(2,3), r_1=2p1=(2,3),r1=2
p_2=(-5,8), r_2=2p2=(−5,8),r2=2
p_3=(-15,0), vec v_3 =(1,2)p3=(−15,0),→v3=(1,2)
Now, given
C_1->norm(p-p_1) = r_1C1→∥p−p1∥=r1
C_2->norm(p-p_2)=r_2C2→∥p−p2∥=r2 and
L_1->p_3+lambda vec v_3L1→p3+λ→v3
find
C->norm(p-p_0) = r_0C→∥p−p0∥=r0
such that
CC is tangent to C_1,C_2C1,C2and L_1L1
Here p = (x,y)p=(x,y) and p_0=(x_0,y_0)p0=(x0,y0)
We can stablish the following retationships
norm(p_0-p_1)=r_0+r_1∥p0−p1∥=r0+r1
norm(p_o-p_2)=r_0+r_2∥po−p2∥=r0+r2
if p_t in L_1pt∈L1 is a tangency point then
<< p_t-p_0, vec v_3 >> = 0⟨pt−p0,→v3⟩=0
norm(p_t-p_0)= r_0∥pt−p0∥=r0
where
p_t = p_3+lambda vec v_3pt=p3+λ→v3
Finally we get the following equations
{
(<< p_3+lambda vec v_3-p_0,vec v_3 >> = 0),
(norm(p_3+lambda vec v_3-p_0)=r_0),
(norm(p_0-p_1)=r_0+r_1),
(norm(p_0-p_2)=r_0+r_2)
:}
so we have four equations and four incognitas x_0,y_0,lambda,r_0
Solving we obtain
((r_0 = 8.17665, x_0 = -6.86077, y_0 = -2.00508, lambda = 0.825813),
(r_0 = 11.6327, x_0 = 6.01912, y_0 = 16.0268,
lambda = 10.6145))
Attached the figure with the solutions in red and the initial geometric elements in black.