grandes-ecoles 2023 Q10

grandes-ecoles · France · x-ens-maths-a__mp Groups Subgroup and Normal Subgroup Properties
a) Deduce that $\alpha(S \times S) = \mathrm{SO}(\mathbb{H})$. b) Show that $N := \alpha(S \times \{E\})$ is a subgroup of $\mathrm{SO}(\mathbb{H})$, then that $gng^{-1} \in N$ for all $n \in N$ and $g \in \mathrm{SO}(\mathbb{H})$ and that $\{\pm\mathrm{id}\} \subsetneq N \subsetneq \mathrm{SO}(\mathbb{H})$.
a) Deduce that $\alpha(S \times S) = \mathrm{SO}(\mathbb{H})$.\\
b) Show that $N := \alpha(S \times \{E\})$ is a subgroup of $\mathrm{SO}(\mathbb{H})$, then that $gng^{-1} \in N$ for all $n \in N$ and $g \in \mathrm{SO}(\mathbb{H})$ and that $\{\pm\mathrm{id}\} \subsetneq N \subsetneq \mathrm{SO}(\mathbb{H})$.