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A common tangent is a line which is tangent to two (or more) curves.
From the definition of tangent, it can ONLY have one point in common called the tangent point.
Tangent, in geometry, is used to describe when figures have only one point in common.
In Trig. tangent is applied to triangles.
the length of thr direct common tangent will be 2*{1/2 power of (r1*r2)}
the answer will be 8 units in this case...
tangent