In mathematics, a straight line is defined as a line followed by a point travelling in a constant direction with no curvature. Straight lines connect two points shortest distance.
Lines can be divided into many types, such as horizontal, perpendicular, vertical, and parallel.
When a line moves from east to west, it is horizontal.
When any two lines meet each other at an angle of 90° is called a perpendicular line.
A straight line from up to down is called a vertical line.
When any two lines don't meet, touch, or intersect even at infinity, that line is called a parallel line.
A straight line that touches the curve is called a tangent at any given point.
An angle is formed when two rays are united at a common point. An angle is usually measured in degrees, radians, or gradians.