What is a right sided figure?

Answer 1

.Four sided figures are called quadrilaterals.

A quadrilateral with opposite sides equal and parallel is called a parallelogram. The corresponding solid is called a parallelepiped. A parallelogram, with all its angles right angles is called a rectangle. The solid version of the rectangle is called a cuboid. A rectangle with all its sides equal is called a square, which is, in 3d, a cube.

The triangle creeps into this page because we need to know its area in order to compute the area of a trapezoid.

A quadrilateral with only two of its sides parallel is called a trapezium, or trapezoid. There is a confusing difference in meaning between the USA and elsewhere with these terms, where a trapezium in the USA means a quadrilateral with no sides parallel.

Proclus, who wrote the commentaries for Euclid's Elements, called a trapezium figure with exactly two sides parallel, and a trapezoid one with no sides parallel. However, in 1795, Hutton's Mathematical Dictionary accidentally reversed the two definitions, and in USA and other countries, the trapezium became a trapezoid and the trapezoid became a trapezium. (See this site)