Common Denominator
Definition of Common Denominator
A tangent that is common to two circles and does not intersect the segment joining the centers of the circles is called Common External Tangent.
More About Common Denominator

A common tangent can either be a common external tangent or a common internal tangent.
Video Examples:How to Construct a Common Tangent of Two Circles : Math Instructi
Example of Common Denominator
In the above figure, line PQ is the common external tangent.
In the above figure, line AB is the common external tangent.
Solved Example onCommon Denominator
Ques:
Identify the common external tangent from the given figure.
Choices:
A. ABB. CD
C. EF
D. none of the above
Correct Answer: B
Solution:

Step 1: A tangent that is common to two circles and does not intersect the segment joining the centers of the circles is called common external tangent.
Step 2: In the given figure, the line CD touches both the circles on the same side of the line is the external tangent to the circle.
Step 3: So, CD is the common external tangent line.
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