Students will develop a robot that can draw different types of triangles with a laser pointer. Prior to the project, students should have knowledge of how triangles can be categorized based on their angles and side lengths. In the lesson, students use reasoning to find possible solutions and document their work.


It is a prerequisite for the project that students are familiar with equilateral, isosceles, right-angled, obtuse and acute triangles.


  • Joint module (Fable robot)
  • LEGO to build a holder for the laser pointer
  • Laser pointer
  • PC
  • Pen and paper (possibly Geogebra or similar program)

Subject & grade: Math, Grade 4-6

Duration: 2-4 lessons


Learning activities

Students work in groups of 2-3. Each group receives a copy of the assignment sheet.

Students develop code for Fable to make the module draw different kinds of triangles with a laser pointer. Students document their triangles by drawing them. To do this, they can use a sheet of a paper as the work surface for the laser pointer. Students mark each corner point (laser dot) and draw the figure by connecting the points with lines. Students will probably realize that they need to include pauses in their code in order to have time to mark the points on the paper.

The project can be taken further by challenging students to write a code where the robot solely draws random triangles. This can also be used as an option for differentiation if coding skills vary among the student groups.

Code example

In the file overview, there is a code example for a right-angled triangle. In the example, the laser is attached in the same way as shown in the illustration. The space bar will start the program and the laser will follow a trajectory that creates a right-angled triangle. Pauses have been included in the code so there is time to mark the laser’s position at the corner points.


Students prepare a presentation in which they describe how they solved the assignment for one of the triangles drawn.

In addition, students complete a self-evaluation form. The form can be used by the teacher to respond to any questions in connection with the project’s conclusion or as the basis for planning the next lesson.

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