NIMCET 2012 — Mathematics PYQ
NIMCET | Mathematics | 2012If θ(0≤θ≤π) is the angle between the vectors a and b, then a⋅b∣a×b∣ is equal to:
Choose the correct answer:
- A.
−cotθ
- B.
tanθ
(Correct Answer) - C.
−tanθ
- D.
cotθ
tanθ
Explanation
1. Recall the Formulas:
-
Magnitude of Cross Product: The magnitude of the cross product a×b is given by:
∣a×b∣=∣a∣∣b∣sinθ -
Dot Product: The dot product a⋅b is given by:
a⋅b=∣a∣∣b∣cosθ
2. Substitute into the Given Expression:
We need to find the value of a⋅b∣a×b∣:
3. Simplify the Expression:
The magnitudes ∣a∣ and ∣b∣ cancel out from the numerator and the denominator:
Conclusion:
The expression a⋅b∣a×b∣ simplifies to tanθ.
Correct Option:
(b) tanθ
Explanation
1. Recall the Formulas:
-
Magnitude of Cross Product: The magnitude of the cross product a×b is given by:
∣a×b∣=∣a∣∣b∣sinθ -
Dot Product: The dot product a⋅b is given by:
a⋅b=∣a∣∣b∣cosθ
2. Substitute into the Given Expression:
We need to find the value of a⋅b∣a×b∣:
3. Simplify the Expression:
The magnitudes ∣a∣ and ∣b∣ cancel out from the numerator and the denominator:
Conclusion:
The expression a⋅b∣a×b∣ simplifies to tanθ.
Correct Option:
(b) tanθ

