Be a geometer with Dr. Geo: construct and manipulate interactive geometric models. Learn geometry (and physics, too!) visually and interactively.

- Construct quadrilaterals and explore the properties of the
parallelogram, rectangle, rhombus or square.
- Draw a triangle and its circumscribing circle, then drag one of its
corners slowly to cross the opposite side. Visually observe why a
straight line is an "infinite circle". Get junior high school kids
motivated with the idea of "crosscap" in projective geometry and
topology.
- Learn about the symmetry you can find in car logos.
- Understand why the measures of the interior angles of a triangle
always add up to 180 degrees.
- Visualize the properties of the rectangle, isosceles or equilateral
triangles.
- Understand how a Newtonian telescope works and play with its model.
- Play with the Trammel of Archimedes to draw ellipse.
- Draw an ellipse, then drag one of its focii, and watch how it
gradually becomes a hyperbola.
- Move the focus of a lens in a Dr. Geo sketch, and learn how a real
inverted image morphs into a virtual upright image. Use the macro
function to stack two lens and create your microscope in Dr. Geo.
- Discover how Eratosthenes calculated the circumference of the Earth.

Plus many more to explore or to create yourself.


All in all Dr. Geo is an interactive geometry application. It allows one to create a geometric model you can manipulate according to its constraints. It is usable at home or at school, in primary or secondary education level. With the free Desktop version, you can also construct very elaborated sketches to share with your friends, students or kids on tablet.

With Dr. Geo you construct:
- free point, mobile point on a curve, intersection point, point at
the middle of two points, or segment middle.
- line, parallel line, perpendicular line, perpendicular bisector,
angle bisector, ray, segment, vector, circle, arc, polygon, locus.
- geometric transformation: symmetry, reflection, translation,
homothety (scale).
- distance between objects, length, coordinates, equations, free text.
- macro-construction: teach Dr. Geo how to construct complex objects
for you.

When constructing an object, Dr. Geo deduces from your construction sequence the exact nature of the object you want to construct.

For example, to construct a circle, you can:
1. select two points then Dr. Geo constructs a circle defined by its
center and a point it goes through.
2. select one point and a segment then Dr. Geo constructs a circle
defined by its center and a radius equal to the segment's length.
3. select one point and a value then Dr. Geo constructs a circle
defined by its center and a radius equal to the value.

When necessary, Dr. Geo constructs for you, on the fly, intermediate point(s): free on the sketch, mobile on a curve or at the intersection of two curves.