The GATE Grind

GATE 2023 MA – Question 18

Topology · Connectedness and Compactness · 1 mark · Multiple choice

In usual ℝ², X={(x,x sin(1/x)):0<x≤1}∪({0}×ℝ) and Y={(x,sin(1/x)):0<x≤1}∪({0}×ℝ). P:X is connected. Q:Y is connected. Choose truth values.

  1. Both P and Q true
  2. P false, Q true
  3. P true, Q false
  4. Both false

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (A) Both P and Q true

Explanation

Each graph is a continuous image of (0,1] and hence connected; so is its closure. The first closure meets the vertical axis at (0,0), and the second along {0}×[−1,1]. Union with the connected vertical line therefore remains connected in both cases. **A**. Path connectedness is a different property and is not asked.

More Connectedness and Compactness questions

All Connectedness and Compactness questions →