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question:Khaani Write 2 line for review for this pakistani ost
answer:"Khaani, a hauntingly beautiful OST that tugs at the heartstrings with its poignant lyrics The soulful melody and emotive vocals make it a standout track that lingers long after listening"
question:перефразируй The secret to a fabulous hairstyle when you have natural hair is keeping your mane protected from the harsh sun. No need to worry as here are the trendiest and most fashionable protective African American hairstyles on the internet this season!
answer:If you have natural hair, the key to achieving a fabulous hairstyle is ensuring your mane is shielded from the damaging effects of the sun. Don't fret, as we have compiled a list of the most stylish and trendy protective hairstyles for African Americans available online this season!
question:Prove that R^2 is not homeomorphic to S^2
answer:To prove that (mathbb{R}^2) (the Euclidean plane) is not homeomorphic to (S^2) (the 2-dimensional sphere), we need to show that there is no continuous bijection between them whose inverse is also continuous. A homeomorphism is a bijective continuous function between two topological spaces with a continuous inverse. If we can show that some topological property is preserved under homeomorphisms and that property differs between (mathbb{R}^2) and (S^2), it will imply there can be no homeomorphism between these spaces. One such property is compactness. A topological space is compact if every open cover of the space has a finite subcover. The sphere (S^2) is compact because it is closed (contains all its limit points) and bounded in (mathbb{R}^3), and by the Heine-Borel theorem, a subset of (mathbb{R}^n) is compact if and only if it is closed and bounded. However, (mathbb{R}^2) is not compact because it is not bounded (it extends infinitely in all directions), and thus there exist open covers with no finite subcover. Since compactness is preserved by homeomorphisms and (mathbb{R}^2) is not compact while (S^2) is, it follows that there can be no homeomorphism between (mathbb{R}^2) and (S^2). Therefore, the two spaces are not homeomorphic.
question:Do homeomorphisms preverve compactness
answer:Yes, homeomorphisms preserve compactness. If two spaces are homeomorphic to each other, then either both are compact, or neither is. This property reliability facilitates the use of compactness as a topological invariant to demonstrate that two spaces are not homeomorphic. Here's why compactness is preserved: - If a space (X) is compact and there is a homeomorphism (f: X to Y), then the image of (X) under (f) (which is the entire space (Y)) will also be compact. This is because compactness is preserved under continuous images, and a homeomorphism is, by definition, a continuous bijection. In other words, (f) takes compact sets in (X) to compact sets in (Y). - Conversely, the inverse (f^{-1}: Y to X) is also a continuous function since (f) is a homeomorphism. So, if (Y) is compact, then the image of (Y) under (f^{-1}) (the entire space (X)) must also be compact. These facts ensure that compactness is a topological property preserved by homeomorphisms. If one space is compact and the other is not, this difference is enough proof to conclude that the spaces cannot be homeomorphic.