Tangent - Tangent Circles

Tangent Circles

Two circles of non-equal radius, both in the same plane, are said to be tangent to each other if they meet at only one point. Equivalently, two circles, with radii of r_i and centers at (x_i, y_i), for i = 1, 2 are said to be tangent to each other if

• Two circles are externally tangent if the distance between their centres is equal to the sum of their radii.

• Two circles are internally tangent if the distance between their centres is equal to the difference between their radii.