Which of the following statement patterns is a contradiction? \[ \begin{aligned} S_1 &: (p \to q) \land (p \land \sim q) \\ S_2 &: [p \land (p \to q)] \to q \\ S_3 &: (p \lor q) \to \sim p \\ S_4 &: [p \land (p \to q)] \leftrightarrow q \end{aligned} \]
If \[ y = \cot^{-1}\!\left(\sqrt{\frac{1-\sin x}{1+\sin x}}\right), \quad \text{then find} \quad \frac{dy}{dx}. \]
If the L.M.V.T. holds for the function \( f(x) = x + \dfrac{1}{x} \), \(x \in [1,3]\), then \(c =\)
If\[ A = \begin{bmatrix} \cos\theta & -\sin\theta \\ -\sin\theta & -\cos\theta \\ \end{bmatrix} \] then \(A^{-1} =\)