1.
If Δ1=xsinθcosθsinθx1cosθ1x\Delta_1 = \begin{vmatrix} x & \sin\theta & \cos\theta \\ -\sin\theta & -x & 1 \\ \cos\theta & 1 & x \end{vmatrix} and Δ2=xsin2θcos2θsin2θx1cos2θ1x\Delta_2 = \begin{vmatrix} x & \sin 2\theta & \cos 2\theta \\ -\sin 2\theta & -x & 1 \\ \cos 2\theta & 1 & x \end{vmatrix}, x0x \neq 0; then for all θ(0,π2)\theta \in \left(0, \dfrac{\pi}{2}\right):