2. TRIANGLE POWER

These days, great power pylons are a common sight, striding across hills and valleys, linked by their joining cables. I often wonder at the stresses and strains placed on these massive structures. The key to their strength lies in the humble triangle. Look at the adjacent picture, and take a rough count of the number of triangles used in the building of this pylon.

The triangle has the property of rigidity. Think of the edges of a polygon in the plane as being rigid, but the vertices as hinges, allowing the polygon to change shape. If the polygon is a triangle, no movement within the plane is possible. Is this true for any other polygon? If we have a polygon of n sides (n > 3) we can make it rigid by adding a certain number of rigid struts. How many? Ask some questions of your own.

    

   – Ian Britton – FreeFoto.com