Metamath Proof Explorer


Theorem sqrtcvallem2

Description: Equivalent to saying that the square of the imaginary component of the square root of a complex number is a nonnegative real number. Lemma for sqrtcval . See imsqrtval . (Contributed by RP, 11-May-2024)

Ref Expression
Assertion sqrtcvallem2
|- ( A e. CC -> 0 <_ ( ( ( abs ` A ) - ( Re ` A ) ) / 2 ) )

Proof

Step Hyp Ref Expression
1 abscl
 |-  ( A e. CC -> ( abs ` A ) e. RR )
2 recl
 |-  ( A e. CC -> ( Re ` A ) e. RR )
3 1 2 resubcld
 |-  ( A e. CC -> ( ( abs ` A ) - ( Re ` A ) ) e. RR )
4 2rp
 |-  2 e. RR+
5 4 a1i
 |-  ( A e. CC -> 2 e. RR+ )
6 releabs
 |-  ( A e. CC -> ( Re ` A ) <_ ( abs ` A ) )
7 1 2 subge0d
 |-  ( A e. CC -> ( 0 <_ ( ( abs ` A ) - ( Re ` A ) ) <-> ( Re ` A ) <_ ( abs ` A ) ) )
8 6 7 mpbird
 |-  ( A e. CC -> 0 <_ ( ( abs ` A ) - ( Re ` A ) ) )
9 3 5 8 divge0d
 |-  ( A e. CC -> 0 <_ ( ( ( abs ` A ) - ( Re ` A ) ) / 2 ) )