There are lots of different types of polygon. Find out about quadrilaterals, triangles, polygons and circles in this KS2 Maths guide from BBC Bitesize.

The triangle is a small instrument made of a metal rod bent into a triangle shape that is open at one corner. While small, its sound is distinct, with multiple overtones and nonharmonic resonance.

For the triangle, researchers captured proof that resonance occurs even with the notched, open corner, and it may occur in other instrument shapes as well. WASHINGTON, May 6, 2025 – The triangle ...