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Step * of Lemma r-triangle-inequality

∀[x,y:ℝ].  (|x + y| ≤ (|x| + |y|))
BY
{ (Auto THEN Unfold `rleq` 0 THEN (RWO "rnonneg-iff" 0 THENA Auto)) }

1
1. x : ℝ
2. y : ℝ
⊢ rnonneg2((|x| + |y|) - |x + y|)

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Latex:

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Latex:
\mforall{}[x,y:\mBbbR{}].    (|x  +  y|  \mleq{}  (|x|  +  |y|))


By

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Latex:
(Auto  THEN  Unfold  `rleq`  0  THEN  (RWO  "rnonneg-iff"  0  THENA  Auto))

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