You may also like

problem icon

Center Path

Four rods of equal length are hinged at their endpoints to form a rhombus. The diagonals meet at X. One edge is fixed, the opposite edge is allowed to move in the plane. Describe the locus of the point X and prove your assertion.

problem icon

Tied Up

In a right angled triangular field, three animals are tethered to posts at the midpoint of each side. Each rope is just long enough to allow the animal to reach two adjacent vertices. Only one animal can reach all points in the field. Which one is it and why?

problem icon

The Cyclic Quadrilateral

This gives a short summary of the properties and theorems of cyclic quadrilaterals and links to some practical examples to be found elsewhere on the site.

Right Angles

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2
The problem Triangles in Circles will help if you are having difficulty calculating angles.

Try an even number of points round the edge.

Proving this will be easier if you join all the points to the centre and look for isosceles triangles.