MCQ
Solve x2 + 1 = 0.
- Ax = 1, -1
- Bx = i, -i
- Cx = -1
- Dx = i
Solution:
$\text{x}^2 + 1 = 0$
$\Rightarrow\text{x}^2=-1\Rightarrow\text{x}$
$=\pm\sqrt{-1}=\pm\text{i}$
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$\cos2\theta\cos2\phi+\sin^2(\theta-\phi)-\sin^2(\theta+\phi)$ is equal to:
$\sin2(\theta+\phi)$
$\cos2(\theta+\phi)$
$\sin2(\theta-\phi)$
$\cos2(\theta-\phi)$
[Hint: Use
$\sin^2\text{A}-\sin^2\text{B}=\sin(\text{A+B})\sin(\text{A}-\text{B})$]