JEE Main202118 Mar 2021Evening ShiftMathematicsVector AlgebraActual
Let a → and b → be two non-zero vectors perpendicular to each other and | a → | = | b → | , If | a → × b → | = | a → | , then the angle between the vectors ( a → + b → + ( a → × b → ) ) and a → is equal to :
Options
- Asin - 1 1 3
- Bcos - 1 1 3
- Ccos - 1 1 2
- Dsin - 1 1 6
Correct answer
B. cos - 1 1 3
Step-by-step solution
| a → | = | b → | , | a → × b → | = | a → | , a → ⊥ b → | a → × b → | = | a → | ⇒ | a → | | b → | sin 90 ° = | a → | ⇒ | b → | = 1 = | a → | a → and b → are mutually perpendicular unit vectors. Let a → = i ^ , b → = j ^ ⇒ a → × b → = k ^ cos θ = ( i ^ + j ^ + k ^ ) i ^ 3 1 = 1 3 ⇒ θ = cos - 1 1 3