a → , b → & c → are three vectors such that | a → | = 3 , | b → | = 5 , | c → | = 7 If a ¯ , b ¯ , c ¯ are perpendicular to the vectors b → + c → , c → + a → , a → + b → respectively, then a → + b → + c → 2 - 2 =

Step-by-step solution

Given, | a → | = 3 ,   | b → | = 5 ,   | c → | = 7 Now, a → ⊥ b → + c → . Therefore, a → · b → + c → = 0 a → · b → + a → · c → = 0     . . . i Similarly, b → · c → + a → = 0 ⇒ b → · c → + b → · a → = 0     . . . ii   c → · a → + b → = 0 ⇒ c → · a → + c → · b →