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

      example of Common External Tangent

    In the above figure, line PQ is the common external tangent.
      example of 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.
    example of Common External Tangent

    Choices:
    A. AB
    B. 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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