NIMCET 2011 — Mathematics PYQ
NIMCET | Mathematics | 2011The general value of θ satisfying the equation 2sin2θ−3sinθ−2=0 is:
Choose the correct answer:
- A.
nπ+(−1)n6π
- B.
nπ+(−1)n2π
nπ+(−1)n67π
Explanation
1. Factorize the quadratic equation:
Let sinθ=t. The equation becomes 2t2−3t−2=0.
2. Solve for t:
-
t=2⟹sinθ=2 (Not possible as ∣sinθ∣≤1)
-
2t+1=0⟹t=−21⟹sinθ=−21
3. Find the general solution:
sinθ=−21=sin(−6π)
The general solution for sinθ=sinα is θ=nπ+(−1)nα.
This is equivalent to θ=nπ+(−1)n67π as sin(67π)=−21.
Correct Option: (d)
Explanation
1. Factorize the quadratic equation:
Let sinθ=t. The equation becomes 2t2−3t−2=0.
2. Solve for t:
-
t=2⟹sinθ=2 (Not possible as ∣sinθ∣≤1)
-
2t+1=0⟹t=−21⟹sinθ=−21
3. Find the general solution:
sinθ=−21=sin(−6π)
The general solution for sinθ=sinα is θ=nπ+(−1)nα.
This is equivalent to θ=nπ+(−1)n67π as sin(67π)=−21.
Correct Option: (d)
