( x ) Coplanar Vectors A system of vectors is said to be coplanar , if their supports are parallel to the same plane . Otherwise they are called noncoplanar vectors .
( xi ) Reciprocal of a Vector A vector having the same direction as that of a given vector but magnitude equal to the reciprocal of the given vector is known as the reciprocal of a .
i . e ., if | a | = a , then | a -1 | = 1 / a .
Addition of Vectors
Let a and b be any two vectors . From the terminal point of a , vector b is drawn . Then , the vector from the initial point O of a to the terminal point B of b is called the sum of vectors a and b and is denoted bya + b . This is called the triangle law of addition of vectors .
Parallelogram Law
Let a and b be any two vectors . From the initial point of a , vector b is drawn and parallelogram OACB is completed with OA and OB as adjacent sides . The vector OC is defined as the sum of a and b . This is called the parallelogram law of addition of vectors .
The sum of two vectors is also called their resultant and the process of addition as composition .