Mathematics for IGCSE & O level - Circle Theorems (Section 2 - No. 35)
What can be concluded if two circles touch externally?
Their centres are equidistant.
Their common tangent passes through the point of contact.
The distance between their centers is the sum of their radii.
They cannot be connected by a line.
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When two circles touch externally, the distance between their centers is equal to the sum of their radii, and the centers lie on a line through the point of contact.