Question Number 346 by 123456 last updated on 25/Jan/15
$$\Gamma\left(\theta\right)=\begin{bmatrix}{\mathrm{cos}\:\theta}&{\mathrm{sin}\:\theta}\\{−\mathrm{sin}\:\theta}&{\mathrm{cos}\:\theta}\end{bmatrix} \\ $$$$\Lambda\left(\theta,{t}\right)=\begin{bmatrix}{\mathrm{cos}\:\theta}&{\mathrm{sinh}\:{t}\:\mathrm{sin}\:\theta}\\{\mathrm{sin}\:\theta}&{\mathrm{cosh}\:{t}\:\mathrm{cos}\:\theta}\end{bmatrix} \\ $$$$\zeta\left(\theta,{t}\right)=\Gamma\left(\theta\right)×\Lambda\left(\theta,{t}\right)+\Lambda\left(\theta,{t}\right)×\Gamma\left(\theta\right) \\ $$$$\zeta\left(\theta,\mathrm{0}\right)=? \\ $$$$\mathrm{det}\:\zeta\left(\theta,\mathrm{0}\right)=? \\ $$
Answered by prakash jain last updated on 23/Dec/14
$$\Lambda\left(\theta,\mathrm{0}\right)=\begin{bmatrix}{\mathrm{cos}\:\theta}&{\mathrm{0}}\\{\mathrm{sin}\:\theta}&{\mathrm{cos}\:\theta}\end{bmatrix} \\ $$$$\Gamma\left(\theta\right)×\Lambda\left(\theta,\mathrm{0}\right)=\begin{bmatrix}{\mathrm{cos}^{\mathrm{2}} \theta+\mathrm{sin}^{\mathrm{2}} \theta}&{\mathrm{0}+\mathrm{cos}\:\theta\mathrm{sin}\:\theta}\\{−\mathrm{sin}\:\theta\mathrm{cos}\:\theta+\mathrm{sin}\:\theta\mathrm{cos}\:\theta}&{\mathrm{cos}^{\mathrm{2}} \theta}\end{bmatrix} \\ $$$$=\begin{bmatrix}{\mathrm{1}}&{\mathrm{cos}\:\theta\mathrm{sin}\:\theta}\\{\mathrm{0}}&{\mathrm{cos}^{\mathrm{2}} \theta}\end{bmatrix} \\ $$$$\Lambda\left(\theta,\mathrm{0}\right)×\Gamma\left(\theta\right)=\begin{bmatrix}{\mathrm{cos}^{\mathrm{2}} \theta+\mathrm{0}}&{\mathrm{cos}\:\theta\mathrm{sin}\:\theta+\mathrm{0}}\\{\mathrm{cos}\:\theta\mathrm{sin}\:\theta−\mathrm{sin}\:\theta\mathrm{cos}\:\theta}&{\mathrm{1}}\end{bmatrix} \\ $$$$=\begin{bmatrix}{\mathrm{cos}^{\mathrm{2}} \theta}&{\mathrm{cos}\:\theta\mathrm{sin}\:\theta}\\{\mathrm{0}}&{\mathrm{1}}\end{bmatrix} \\ $$$$\Gamma\left(\theta\right)×\Lambda\left(\theta,\mathrm{0}\right)+\Lambda\left(\theta,\mathrm{0}\right)×\Gamma\left(\theta\right)=\begin{bmatrix}{\mathrm{1}+\mathrm{cos}^{\mathrm{2}} \theta}&{\mathrm{2cos}\:\theta\mathrm{sin}\:\theta}\\{\mathrm{0}}&{\mathrm{1}+\mathrm{cos}^{\mathrm{2}} \theta}\end{bmatrix} \\ $$$$\zeta\left(\theta,\mathrm{0}\right)=\begin{bmatrix}{\mathrm{1}+\mathrm{cos}^{\mathrm{2}} \theta}&{\mathrm{2cos}\:\theta\mathrm{sin}\:\theta}\\{\mathrm{0}}&{\mathrm{1}+\mathrm{cos}^{\mathrm{2}} \theta}\end{bmatrix} \\ $$$$\mathrm{det}\:\zeta\left(\theta,\mathrm{0}\right)=\left(\mathrm{1}+\mathrm{cos}^{\mathrm{2}} \theta\right)^{\mathrm{2}} \\ $$