Note: Desmos and GeoGebra now both offer SVG export options, which can then be rendered in Tinkercad. The tweets below are for "historical" reference only.
Desmos:
GeoGebra:
This file includes a cone and four other cones that have been sliced to show the possible cross-sections.
This puzzle is challenges the user to assemble the pieces into a dodecagon, then into a square. First designed in GeoGebra (https://www.geogebra.org/m/rcxmjfyv) .
Source = http://www.puzzles.com/PuzzlePlayground/DodecagonToSquareDissection/DodecagonToSquareDissection.htm
This puzzle is an illusion using four identical pieces to form two different shapes. First designed in GeoGebra (https://www.geogebra.org/m/hf7gkfvc) .
Math Art designed in GeoGebra (https://www.geogebra.org/m/vwdjhhj5).
Math Art designed in GeoGebra (https://www.geogebra.org/m/cdugm3vq).
Logo Designed for The Hewitt School. Designed in Desmos (https://www.desmos.com/calculator/7ar0wdblod).
Twitter Thread = https://twitter.com/shskaercher/status/994358437432741900
Polyhedron designed in GeoGebra (https://www.geogebra.org/m/gx2y7xq5).
Knot designed in GeoGebra (https://www.geogebra.org/m/xfb5d9at).
Block letter S tag. Designed in Desmos (https://www.desmos.com/calculator/b4u0hxtjyi).
Lissajous Graph designed first in Desmos (https://www.desmos.com/calculator/4lil6man6i).
Lissajous Graph designed first in Desmos (https://www.desmos.com/calculator/4lil6man6i).
Directions (You will need a Merge Cube, the Merge Object Viewer mobile app, and a Miniverse account):