A straight line is a curve such that every point on the line segment joining any two points on it lies on it. The theorem states that every first-degree equation in x, y represents a straight line. When we say that a first degree equation in x, y i.e., ax + by + c = 0 represents a line, it means that all points (x,y) satisfying ax + by + c = 0 lie along a line. Thus, a line is also defined as the locus of a point satisfying the condition ax + by + c = 0 where a, b, c are constants. Thus, in order to determine a line, we will need two conditions to determine the two unknown.
The trigonometrical tangent of the angle that a line makes with the positive direction of the x-axis in an anticlockwise sense is called the slope or gradient of the line. Learn about to how to find out the slope of a line in terms of coordinates of any two point on it. Practise the solved examples and learn about how to find angles between lines, various conditions of parallelism of lines and conditions of perpendicularity of two lines. In further exercise, we will be discussing intercepts of a line and different forms of an equation of a straight line. Learn these concepts easily by practicing the questions from the exercises given in RD Sharma solution for the chapter “Straight Lines”.
Chapter 23 The Straight Lines