This article gives an wonderful insight into students working on the Arclets problem that first appeared in the Sept 2002 edition of the NRICH website.

The three corners of a triangle are sitting on a circle. The angles are called Angle A, Angle B and Angle C. The dot in the middle of the circle shows the centre. The counter is measuring the size. . . .

A floor is covered by a tessellation of equilateral triangles, each having three equal arcs inside it. What proportion of the area of the tessellation is shaded?

Can you explain why it is impossible to construct this triangle?

Investigate the different ways of cutting a perfectly circular pie into equal pieces using exactly 3 cuts. The cuts have to be along chords of the circle (which might be diameters).

Measure the two angles. What do you notice?

Draw some quadrilaterals on a 9-point circle and work out the angles. Is there a theorem?

Can you work out how these polygon pictures were drawn, and use that to figure out their angles?

Draw some stars and measure the angles at their points. Can you find and prove a result about their sum?

Semi-regular tessellations combine two or more different regular polygons to fill the plane. Can you find all the semi-regular tessellations?

The graph below is an oblique coordinate system based on 60 degree angles. It was drawn on isometric paper. What kinds of triangles do these points form?

Creating designs with squares - using the REPEAT command in LOGO. This requires some careful thought on angles

Drawing the right diagram can help you to prove a result about the angles in a line of squares.

Interior angles can help us to work out which polygons will tessellate. Can we use similar ideas to predict which polygons combine to create semi-regular solids?

This LOGO Challenge emphasises the idea of breaking down a problem into smaller manageable parts. Working on squares and angles.

Are these statements always true, sometimes true or never true?

Turn through bigger angles and draw stars with Logo.

What is the relationship between the angle at the centre and the angles at the circumference, for angles which stand on the same arc? Can you prove it?

Show that among the interior angles of a convex polygon there cannot be more than three acute angles.

How can you make an angle of 60 degrees by folding a sheet of paper twice?

More Logo for beginners. Learn to calculate exterior angles and draw regular polygons using procedures and variables.

Billy's class had a robot called Fred who could draw with chalk held underneath him. What shapes did the pupils make Fred draw?

Can you find all the different triangles on these peg boards, and find their angles?

Can you find triangles on a 9-point circle? Can you work out their angles?

How would you move the bands on the pegboard to alter these shapes?

Use the interactivity to investigate what kinds of triangles can be drawn on peg boards with different numbers of pegs.