Relation between subspace union and probabilities union

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SUMMARY

The discussion centers on the mathematical relationship between the probability of the union of two events and the dimension of the union of two subspaces in vector spaces. The formulas presented are p(E_1 ∪ E_2) = p(E_1) + p(E_2) - p(E_1 ∩ E_2) for probabilities and dim(V_1 ∪ V_2) = dim(V_1) + dim(V_2) - dim(V_1 ∩ V_2) for vector spaces. The key insight is that both concepts share a common principle of avoiding double counting, as the intersection is included in both components. This principle applies universally to various measures, including counting, dimensions, and volumes.

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  • Understanding of basic probability theory, specifically union and intersection of events.
  • Familiarity with vector space concepts, including dimensions and subspaces.
  • Knowledge of mathematical notation for probabilities and vector spaces.
  • Ability to apply principles of counting and measure theory.
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Damidami
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Today I was reading in a probabilities textbook that the probability of the union of two events is:

p(E_1 \cup E_2) = p(E_1) + p(E_2) - p(E_1 \cap E_2)

and reminded me of the similarity with the dimension of the union of two subspaces of a vector space:

dim(V_1 \cup V_2) = dim(V_1) + dim(V_2) - dim(V_1 \cap V_2)

Question is: is there a theory/generalization that makes two concepts a particular case of this more general theory? (they look very similar so there must be something common with those concepts)

Thanks,
Damián.
 
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The only common concept is the avoidance of a double count. Since the intersection is part of both components, any measure of the components, be it counting, dimensions, volumes or whatever, would add it twice if we added the measures of the components, which is why we have to subtract one of them again.
 

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