Theorem sqrtge0d

Description: The square root of a nonnegative real is nonnegative. (Contributed by Mario Carneiro, 29-May-2016)

	Ref	Expression
Hypotheses	resqrcld.1	⊢ ( 𝜑 → 𝐴 ∈ ℝ )
	resqrcld.2	⊢ ( 𝜑 → 0 ≤ 𝐴 )
Assertion	sqrtge0d	⊢ ( 𝜑 → 0 ≤ ( √ ‘ 𝐴 ) )

Proof

Step	Hyp	Ref	Expression
1		resqrcld.1	⊢ ( 𝜑 → 𝐴 ∈ ℝ )
2		resqrcld.2	⊢ ( 𝜑 → 0 ≤ 𝐴 )
3		sqrtge0	⊢ ( ( 𝐴 ∈ ℝ ∧ 0 ≤ 𝐴 ) → 0 ≤ ( √ ‘ 𝐴 ) )
4	1 2 3	syl2anc	⊢ ( 𝜑 → 0 ≤ ( √ ‘ 𝐴 ) )