The GATE Grind

GATE 2025 MA – Question 45

Real Analysis · Sequences and Series of Functions · 2 marks · Multiple choice

Let W be the real span of all Legendre polynomials. X=C[−1,1] with sup norm, Y=C[−1,1] with L² norm. Where is W dense?

  1. X only
  2. Y only
  3. Both X and Y
  4. Neither

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (C) Both X and Y

Explanation

Legendre polynomials have successive degrees with nonzero leading coefficients, so their span is all polynomials. Weierstrass gives uniform density in C[−1,1]. Also ‖f−p‖₂≤√2‖f−p‖∞, so uniform approximation implies L² approximation. **C**.

More Sequences and Series of Functions questions

All Sequences and Series of Functions questions →