Question

If AB and CD are common tangents to two circles of unequal radii, then ______.

Answer 1

If AB and CD are common tangents to two circles of unequal radii, then AB = CD.

Explanation:

Extend AB and CD to meet at point P. From external point P the two tangents to each circle are equal, so PA = PC and PB = PD. Subtracting gives (PA – PB) = (PC – PD), hence AB = CD.