The radius of a circle is c r=AC= 1.

(x- 1)？ +(y- 1)？ = 1 ?

In circle x? +y？ =r？ On, the tangent of passing point (xo, yo) is xxo+yyo=r?

Point P (2,3) is the tangent L of circle C, 2x+3y = 1.

y=-2x/3+ 1/3

2

Circle c1:x 2+y 2-2mx+4y+m 2-5 = 0, (x-m)? +(y+2)？ =9

Circle C2: x 2+y 2+2x-2my+m 2-3 = 0, (x+ 1)? +(y-m)？ =4

Two circles are circumscribed, and the center distance is equal to the sum of radii; √[(m- 1)？ +(m-2)？ ]=5

m =-2.5

Contains two circles, the center distance is equal to the radius difference; √[(m- 1)？ +(m-2)？ ]= 1

m= 1，2