Reference · Signed rationals
rainbow.math.rational.signed.square-zero
A signed rational whose square is zero is itself zero. signed/square-zero-reflects : x*x ~ 0 -> x ~ 0 For x=(p,n), signed multiplication exposes the two components positive(x*x) = p*p + n*n negative(x*x) = p*n + n*p. Equivalence of x*x with signed zero is therefore the quadratic equality proved by nnrat/quadratic-equality-reflects, modulo the zero padding in the Grothendieck relation. Native and axiom-free.
signed/square-zero-reflects
signed/square-zero-reflects : (value : ℚ) (zero-square : value · value = 0) → value = 0
0 = signed/zero= = signed/equivalent: equality of rational values· = signed/multiplyℚ = signed/SignedRational