Theorem mulge0d

Description: The product of two nonnegative numbers is nonnegative. (Contributed by Mario Carneiro, 27-May-2016)

	Ref	Expression
Hypotheses	leidd.1	$$⊢\phi \to A\in ℝ$$
	ltnegd.2	$$⊢\phi \to B\in ℝ$$
	addge0d.3	$$⊢\phi \to 0\le A$$
	addge0d.4	$$⊢\phi \to 0\le B$$
Assertion	mulge0d	$$⊢\phi \to 0\le AB$$

Proof

Step	Hyp	Ref	Expression
1		leidd.1	$$⊢\phi \to A\in ℝ$$
2		ltnegd.2	$$⊢\phi \to B\in ℝ$$
3		addge0d.3	$$⊢\phi \to 0\le A$$
4		addge0d.4	$$⊢\phi \to 0\le B$$
5		mulge0	$$⊢\left(\left(A\in ℝ\wedge 0\le A\right)\wedge \left(B\in ℝ\wedge 0\le B\right)\right)\to 0\le AB$$
6	1 3 2 4 5	syl22anc	$$⊢\phi \to 0\le AB$$