User:Kc kennylau/sandbox

Theorem
Let $\struct {R, +, \circ}$ be a ring with unity $1_R$.

Let $\paren {-1}_R$ be the additive inverse of $1_R$.

Then:


 * $\paren {-1}_R \circ \paren {-1}_R = 1_R$

Proof
Let $0_R$ be the ring zero of $\left({R, +, \circ}\right)$.

Then: