what are perpendicular lines
In geometry, two lines or planes (or a line and a plane) are considered perpendicular (or orthogonal) to each other if they form congruent adjacent angles (a T-shape). The term may be used as a noun or adjective. Thus, as illustrated, the line AB is the perpendicular to CD through the point A.
By definition, a line is infinitely long, and strictly speaking AB and CD in this example represent line segments of two infinitely long lines. Hence the line segment AB does not have to intersect line segment CD to be considered perpendicular lines, because if the line segments are extended out to infinity, they would still form congruent adjacent angles.
If a line is perpendicular to another as shown, all of the angles created by their intersection are called right angles (right angles measure π/2 radians, or 90°). Conversely, any lines that meet to form right angles are perpendicular.
In a coordinate plane, perpendicular lines have opposite reciprocal slopes. A horizontal line has slope equal to zero while the slope of a vertical line is described as undefined or sometimes ±infinity. Two lines that are perpendicular would be denoted as ABCD
i hope u undrstand........
un1.perpendicular - a straight line at right angles to another line
2.perpendicular - a Gothic style in 14th and 15th century England; characterized by vertical lines and a four-centered (Tudor) arch and fan vaulting
3.perpendicular - a cord from which a metal weight is suspended pointing directly to the earth's center of gravity; used to determine the vertical from a given point
4.perpendicular - an extremely steep face
Adj.1.perpendicular - intersecting at or forming right angles; "the axes are perpendicular to each other"
2.perpendicular - at right angles to the plane of the horizon or a base line; "a vertical camera angle"; "the monument consists of two vertical pillars supporting a horizontal slab"; "measure the perpendicular height"
3.perpendicular - extremely steep; "the great perpendicular face of the cliff"