Let f(x) be a continuous function from R to R such that f(x) = 1 - f(2 - x) Which one of the following options is the CORRECT value of int_0^2 f(x) dx? A. 0 B. 1 C. 2 D. -1

GATE 2024 · Engineering Mathematics · Definite Integral · medium

Answer: 1 (option B)

  1. Integrate the functional equation over [0, 2]: Let I = int_0^2 f(x) dx. Integrating both sides: I = int_0^2 1 dx - int_0^2 f(2-x) dx = 2 - int_0^2 f(2-x) dx.
  2. Apply substitution u = 2 - x to the second integral: int_0^2 f(2-x) dx = int_2^0 f(u)(-du) = int_0^2 f(u) du = I.
  3. Solve for I: Substituting back: I = 2 - I, so 2I = 2 and I = 1.