6.7.1 Different forms of equation of a straight line

. . Different forms of equation of a straight line A straight line can be uniquely fixed if • a point on the straight line and the direction of the straight line are given • two points on the straight line are given We find equations of a straight line in vector and Cartesian form. To find the equation of a straight line in vector form, an arbitrary point P with position vector r  on the straight line is taken and a relation satisfied by r  is obtained by using the given conditions.

This relation is called the vector equation of the straight line. A vector equation of a straight line may or may not involve parameters. If a vector equation involves parameters, then it is called a vector equation in parametric form . If no parameter is involved, then the equation is called a vector equation in non – parametric form .

. . A point on the straight line and the direction of the straight line