### Proposition

The figure below shows
a quadrilateral ABCD, AB = AD, angle ABC = angle ADC = 90 degrees. If AN
and DM are perpendicular, prove that AM and BN are perpendicular.

*This entry contributed by Erina-NJ*.

## Art of Problem 1402, Circle Patterns using iPad Apps

## Geometric Art
using 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.