Horizontal lines run left to right, parallel to the horizon, with slope 0 and equation y = k. Vertical lines run top to bottom, perpendicular to the horizon, with undefined slope and equation x = k.

The base and perpendicular height are at right angles. Showing that a parallelogram has the same area as a rectangle: Split the parallelogram into a right-angled triangle and a trapezium. Move the ...

Scientific American is part of Springer Nature, which owns or has commercial relations with thousands of scientific publications (many of them can be found at www ...

The common method of magnetic disk recording in which vertical bits take up less space than horizontal bits. Also called "vertical recording," Toshiba and Seagate introduced perpendicular recording ...