If a → = 3 2 k ^ , b → = 2 i ^ + 2 j ^ - k ^ 2 , then angle between a → + b → and a → - b → is

Step-by-step solution

Given that, a → = 3 2 k ^ ,   b → = 2 i ^ + 2 j ^ - k ^ 2 ⇒ a → + b → = i ^ + j ^ + k ^ and a → - b → = - i ^ - j ^ + 2 k ^ ⇒ a → + b → = 3 and a → - b → = 6 Let the angle between them is θ , then cos θ = a → + b → · a → - b → a → + b → · a → - b → ⇒ cos θ = - 1 - 1 + 2 3 · 6 ⇒ cos θ = 0 ⇒ θ = 90 °