Monday, July 1, 2013

Common Tangents - Circles with Equal Radius

A. External Tangents
Draw the given circles with centres A and B
  • Draw a line segment joining A and B
  • At A and B construct perpendiculars to AB on its same side to intersect given circles at D and E.
  • Draw a line joining D and E. This line is the required tangent. FG is the other tangent, which can be drawn similarly.
B. Internal Tangents
Draw the given circles with centres P and Q
  • Draw a line segment joining P and Q.
  • Bisect PQ at O. Draw a circle with OP as diameter to cut the circle at M and R.
  • With centre O and radius OM , draw a circle to cut the other circle at S and N.
  • Draw line through M and N. This is the required tangent.
  • Similarly , draw a line through R and S , which is the other required tangent.
This is a Java Applet created using GeoGebra from - it looks like you don't have Java installed, please go to


  1. Hi Sanjay,

    Do you see the applet in your site? I can't see it here.

  2. Thanks for your wonderful tips about writing the circles. It was really useful to me. I am also making the maths related assignment by the help of quality thesis service. In this writing service is provides the high quality papers for their college studies.

  3. Nice post, things explained in details. Thank You.