NIMCET 2011 — Mathematics PYQ
NIMCET | Mathematics | 2011If θ is the angle between a and b and ∣a×b∣=∣a⋅b∣, then θ is equal to:
Choose the correct answer:
- A.
0
- B.
π
- C.
π/2
- D.
π/4
(Correct Answer)
π/4
Explanation
1. Recall the definitions:
-
The magnitude of the cross product is: ∣a×b∣=∣a∣∣b∣sinθ
-
The absolute value of the dot product is: ∣a⋅b∣=∣a∣∣b∣cosθ
2. Set up the equation based on the given condition:
3. Simplify the equation:
Assuming ∣a∣=0 and ∣b∣=0:
4. Solve for θ:
Divide both sides by cosθ:
Since θ is the angle between two vectors, it typically lies in the range [0,π]. The value for which tanθ=1 in this range is:
Conclusion:
The angle between the vectors is π/4.
The correct option is (d).
Explanation
1. Recall the definitions:
-
The magnitude of the cross product is: ∣a×b∣=∣a∣∣b∣sinθ
-
The absolute value of the dot product is: ∣a⋅b∣=∣a∣∣b∣cosθ
2. Set up the equation based on the given condition:
3. Simplify the equation:
Assuming ∣a∣=0 and ∣b∣=0:
4. Solve for θ:
Divide both sides by cosθ:
Since θ is the angle between two vectors, it typically lies in the range [0,π]. The value for which tanθ=1 in this range is:
Conclusion:
The angle between the vectors is π/4.
The correct option is (d).
