Theorem lenltd

Description: 'Less than or equal to' in terms of 'less than'. (Contributed by Mario Carneiro, 27-May-2016)

	Ref	Expression
Hypotheses	ltd.1	$$⊢\phi \to A\in ℝ$$
	ltd.2	$$⊢\phi \to B\in ℝ$$
Assertion	lenltd	$$⊢\phi \to \left(A\le B\leftrightarrow \neg B<A\right)$$

Proof

Step	Hyp	Ref	Expression
1		ltd.1	$$⊢\phi \to A\in ℝ$$
2		ltd.2	$$⊢\phi \to B\in ℝ$$
3		lenlt	$$⊢\left(A\in ℝ\wedge B\in ℝ\right)\to \left(A\le B\leftrightarrow \neg B<A\right)$$
4	1 2 3	syl2anc	$$⊢\phi \to \left(A\le B\leftrightarrow \neg B<A\right)$$