Let $a \in E$ be a non-zero vector and let $\lambda$ and $\mu$ be real numbers. Show that $\tau _ { a } ^ { \mu } \circ \tau _ { a } ^ { \lambda } = \tau _ { a } ^ { \lambda + \mu }$.
Let $a \in E$ be a non-zero vector and let $\lambda$ and $\mu$ be real numbers. Show that $\tau _ { a } ^ { \mu } \circ \tau _ { a } ^ { \lambda } = \tau _ { a } ^ { \lambda + \mu }$.