# RECTANGLE

, in Geometry, is a right-angled parallelogram, or a right-angled quadrilateral figure.

If from any point O, lines be drawn to all the four angles of a Rectangle; then the sum of the squares of the lines drawn to the opposite corners will be equal, in whatever part of the plane the point O is situated; viz, . For other properties of the Rectangle, see Parallelogram; for the Rectangle being a species of the parallelogram, whatever properties belong to the latter, must equally hold in the former.

For the Area of a Rectangle. Multiply the length by the breadth or height.—Otherwise; Multiply the product of the two diagonals by half the sine of their angle at the intersection.

That is, AB X AC, or AD X BC X 1/2 sin. [angle]P = area. A Rectangle, as of two lines AB and AC, is thus denoted, AB X AC, or AB . AC; or else thus expressed, the Rectangle of, or under, AB and AC.

Rectangle

, in Arithmetic, is the same with product or factum. So the Rectangle of 3 and 4, is 3 X 4 or 12; and of a and b is a X b or ab.

· ·

Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

This text has been generated using commercial OCR software, and there are still many problems; it is slowly getting better over time. Please don't reuse the content (e.g. do not post to wikipedia) without asking liam at holoweb dot net first (mention the colour of your socks in the mail), because I am still working on fixing errors. Thanks!