Theorem ltaddpos2

Description: Adding a positive number to another number increases it. (Contributed by NM, 8-Apr-2005)

	Ref	Expression
Assertion	ltaddpos2	$$⊢\left(A\in ℝ\wedge B\in ℝ\right)\to \left(0<A\leftrightarrow B<A+B\right)$$

Proof

Step	Hyp	Ref	Expression
1		ltaddpos	$$⊢\left(A\in ℝ\wedge B\in ℝ\right)\to \left(0<A\leftrightarrow B<B+A\right)$$
2		recn	$$⊢A\in ℝ\to A\in ℂ$$
3		recn	$$⊢B\in ℝ\to B\in ℂ$$
4		addcom	$$⊢\left(A\in ℂ\wedge B\in ℂ\right)\to A+B=B+A$$
5	2 3 4	syl2an	$$⊢\left(A\in ℝ\wedge B\in ℝ\right)\to A+B=B+A$$
6	5	breq2d	$$⊢\left(A\in ℝ\wedge B\in ℝ\right)\to \left(B<A+B\leftrightarrow B<B+A\right)$$
7	1 6	bitr4d	$$⊢\left(A\in ℝ\wedge B\in ℝ\right)\to \left(0<A\leftrightarrow B<A+B\right)$$