Bourbaki

Corollary

Tag 092I, permanent. Cite it as [Bourbaki, Tag 092I].

Integration, V, p. 42, § 5. Measures defined by numerical densities

Let g1g_1 and g2g_2 be two locally μ\mu-integrable numerical functions; then

inf⁡(g1⋅μ,g2⋅μ)=inf⁡(g1,g2)⋅μ;sup⁡(g1⋅μ,g2⋅μ)=sup⁡(g1,g2)⋅μ. \inf(g_1 \cdot \mu, g_2 \cdot \mu) = \inf(g_1, g_2) \cdot \mu ; \quad \sup(g_1 \cdot \mu, g_2 \cdot \mu) = \sup(g_1, g_2) \cdot \mu .

In particular, if gg is a locally μ\mu-integrable numerical function, then

(g⋅μ)+=g+⋅μ;(g⋅μ)−=g−⋅μ. (g \cdot \mu)^+ = g^+ \cdot \mu ; \quad (g \cdot \mu)^- = g^- \cdot \mu .

This follows at once from Prop. 2 and the formulas (6) of Ch. II, §1, No. 1.

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

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Transcribed from the printed volume. Not translated.