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GATE 2025 MA – Question 44

Topology · Topological Spaces and Constructions · 2 marks · Multiple choice

On the unit sphere S⊂ℝ³ identify points exactly when their third coordinates agree. Give the equivalence-class space the quotient topology. To which space is it homeomorphic?

  1. The interval [−1,1]
  2. The unit circle
  3. The closed unit disk
  4. The cylinder x₁²+x₂²=1, −1≤x₃≤1

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Correct answer: (A) The interval [−1,1]

Explanation

Height h(x)=x₃ is continuous and onto [−1,1], with fibers exactly the equivalence classes. It induces a continuous bijection from the compact quotient to the Hausdorff interval, hence a homeomorphism. **A**.

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