# Poster of Geometry Problem 1380: Common Internal Tangents. Circles, Secant, Congruent Chords, iPad Apps

### Proposition

In the figure below,
CD and EF are the common internal tangents to the circles A and B. CF
extended
intersects the circles A and B at G and H, respectively. Prove that the chords
CG and HF are congruent.

*
This entry
contributed by Markus Heisss, Wurzburg, Bavaria. Published in:
"Die Wurzel - Zeitschrift fur Mathematik", Dec. 2005,
www.wurzel.org.*

See solution below

See also:

Original problem
1380.

### Geometric Art using iPad or Mobile Apps

Geometric art is a form of art based on the use and application of geometric figures. A geometric figure is any set or combination of points, lines, surfaces and solids.

A mobile app or mobile application software is a computer program designed to run on smartphones and tablet computers.