- Regular tetrahedron (Wikipedia)
A regular tetrahedron is a tetrahedron in which all four faces are equilateral triangles. In other words, all of its faces are the same size and shape (congruent) and all edges are the same length. A convex polyhedron in which all of its faces are equilateral triangles is the deltahedron. There are eight convex deltahedra, one of which is the regular tetrahedron.
- Frederick the Great (Wikipedia)
Frederick II (German: Friedrich II.; 24 January 1712 – 17 August 1786) was King in Prussia from 1740 until 1772, and King of Prussia from 1772 until his death in 1786. His most significant accomplishments include his military successes in the Silesian wars, his reorganisation of the Prussian Army, the First Partition of Poland, and his patronage of the arts and the Enlightenment. Frederick was the last Hohenzollern monarch titled King in Prussia, declaring himself King of Prussia after annexing Royal Prussia from the Polish–Lithuanian Commonwealth in 1772. Prussia greatly increased its territories and became a major military power in Europe under his rule. He became known as Frederick the Great (German: Friedrich der Große) and was nicknamed “Old Fritz” (German: der Alte Fritz).