Geoboard

Geoboard:
Buttons:
0=0 Insert new rubber band
T Erase rubber band
Col Change rubber band color
A Calculate area

Drag vertices and edges.
Drag all mesh touching thumbtacks.

Zoom mesh with 'pinch zoom'.


Menu:
Square or isometric mesh.

Practice:
Calculate area contained inside the rubber band (only in square mesh).
Pick's Theorem:
A = I + B/2 -1

A = Area
I = Inner dots.
B = Border dots.

Convex, concave polygons, positive or negative areas:
Triangles
Rectangles
Squares
Tilted rectangles
Tilted squares
Tilted triangles
Farey Sunburst