# Geometry Problem 1399: Triangle, Circumcircle, Perpendiculars, Angles, Congruence, Cyclic Quadrilateral

### Proposition

The figure below shows a triangle ABC with the circumcircle O. E is a point on the chord AD and EF, EG, and EH are perpendicular to BC, AC, and AB, respectively. Prove that angles FGH and DCE are congruent.

## 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.

## Hyperbolic Kaleidoscope, Poincare Disk Model

Poincare disk model is a model of 2-dimensional hyperbolic geometry in which the points of the geometry are inside the unit disk, and the straight lines consist of all segments of circles contained within that disk that are orthogonal to the boundary of the disk, plus all diameters of the disk. Read more.