# Inverse Image(Preimage) of Intersection of Sets Proof | Summary and Q&A

39.1K views
December 17, 2014
by
The Math Sorcerer
Inverse Image(Preimage) of Intersection of Sets Proof

## TL;DR

The video explains the concept of inverse images and proves the equality of inverse images of subsets under a function.

## Key Insights

• 😑 The video introduces the concept of inverse images as the pre-images of subsets under a function.
• 🥶 Visual representations aid in understanding the relationship between the domain, co-domain, subsets, and inverse images.
• 🟰 The proof demonstrates that the inverse image of the intersection of subsets is equal to the intersection of the inverse images.
• 😫 Inclusions between sets are used to establish the equality of inverse images.
• ❓ Understanding the notation and definitions is essential in comprehending the proof.
• 📼 The video emphasizes the need to show both inclusions to prove set equality.
• 👻 Pausing the video allows viewers to grasp the content at their own pace.

## Transcript

so we have a function from capital x to Capital y and we have two subsets a b contained in y and we have to prove this equality so proof maybe before we start the proof let me go over what this notation means so if you have say a subset K of capital Y so this is the idea of what this means um what is this set here well this is called the inverse im... Read More

### Q: What is the definition of the inverse image of a subset under a function?

The inverse image of a subset K under a function F is the set of all elements in the domain X that get mapped to K. It is denoted as "F^(-1)(K)" or "F^(-1)(K) = {x in X | F(x) ∈ K}".

### Q: How can we prove the equality of inverse images of two subsets under a function?

To prove that the inverse image of subset A intersected with the inverse image of subset B is equal to the inverse image of the intersection of subsets A and B, we need to show that each set is a subset of the other. This is done by considering an arbitrary element in both sets and proving its inclusion in the other set.

### Q: What does it mean for X to be in the inverse image of a subset under a function?

If X is in the inverse image of a subset K under a function F, it means that F(X) is an element of K. In other words, X is an element in the domain of F, and when mapped by F, it belongs to the subset K.

### Q: Why is it necessary to prove both directions of the equality of inverse images?

It is crucial to prove both directions to establish the equality of the sets. Proving one direction shows that one set is contained in the other, while proving the other direction demonstrates the reverse inclusion, thereby confirming the equation.

## Summary & Key Takeaways

• The video introduces the concept of inverse images and explains how they are related to subsets of a function's codomain.

• The proof demonstrates that the inverse image of the intersection of two subsets is equal to the intersection of the inverse images of those subsets.

• The explanation includes visual representations and definitions to ensure understanding of the concepts being discussed.