Tangents & Touching Circles (Leaving Cert Mathematics): Flashcards

Two circles that intersect at exactly one point

Point of contact

External touching and internal touching

On opposite sides of the tangent

Smaller circle inside the larger circle

Collinear (on a straight line)

$|C_1C_2| = r_1 + r_2$

$|C_1C_2| = |r_1 - r_2|$

Sum of the radii ($r_1 + r_2$)

Difference of the radii ($|r_1 - r_2|$)