Theorem msq11i

Description: The square of a nonnegative number is a one-to-one function. (Contributed by NM, 29-Jul-1999)

	Ref	Expression
Hypotheses	ltplus1.1	$$⊢A\in ℝ$$
	prodgt0.2	$$⊢B\in ℝ$$
Assertion	msq11i	$$⊢\left(0\le A\wedge 0\le B\right)\to \left(AA=BB\leftrightarrow A=B\right)$$

Proof

Step	Hyp	Ref	Expression
1		ltplus1.1	$$⊢A\in ℝ$$
2		prodgt0.2	$$⊢B\in ℝ$$
3		msq11	$$⊢\left(\left(A\in ℝ\wedge 0\le A\right)\wedge \left(B\in ℝ\wedge 0\le B\right)\right)\to \left(AA=BB\leftrightarrow A=B\right)$$
4	2 3	mpanr1	$$⊢\left(\left(A\in ℝ\wedge 0\le A\right)\wedge 0\le B\right)\to \left(AA=BB\leftrightarrow A=B\right)$$
5	1 4	mpanl1	$$⊢\left(0\le A\wedge 0\le B\right)\to \left(AA=BB\leftrightarrow A=B\right)$$