English
If p ≥ 0, then toNNReal(p*q) = toNNReal(p) * toNNReal(q) for all q.
Русский
Если p ≥ 0, то toNNReal(p*q) = toNNReal(p) * toNNReal(q).
LaTeX
$$$$ p \ge 0 \implies \operatorname{toNNReal}(p q) = \operatorname{toNNReal}(p) \cdot \operatorname{toNNReal}(q). $$$$
Lean4
theorem toNNReal_mul {p q : ℝ} (hp : 0 ≤ p) : Real.toNNReal (p * q) = Real.toNNReal p * Real.toNNReal q :=
NNReal.eq <| by simp [mul_max_of_nonneg, hp]