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If f and g are continuous functions in [0, 1] satisfying f(x) = f(a – x) and g(x) + g(a – x) = a, then afgd∫0af(x)⋅g(x)dx is equal to ______. - Mathematics

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Question

If f and g are continuous functions in [0, 1] satisfying f(x) = f(a – x) and g(x) + g(a – x) = a, then `int_0^"a" "f"(x) * "g"(x)"d"x` is equal to ______.

Options

  • `"a"/2`

  • `"a"/2 int_0^"a" "f"(x)"d"x`

  • `int_0^"a" "f"(x)"d"x`

  • `"a" int_0^"a" "f"(x)"d"x`

MCQ
Fill in the Blanks
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Solution

If f and g are continuous functions in [0, 1] satisfying f(x) = f(a – x) and g(x) + g(a – x) = a, then `int_0^"a" "f"(x) * "g"(x)"d"x` is equal to `"a"/2 int_0^"a" "f"(x)"d"x`.

Explanation:

Since I = `int_0^"a" "f"(x) * "g"(x)"d"x`

= `int_0^"a" "f"("a" - x) "g"("a" - x)"d"x`

= `int_0^"a" "f"(x)("a" - "g"(x))"d"x`

= `"a" int_0^"a" "f"(x) "d"x - int_0^"a" "f"(x) * "g"(x)"d"x`

= `"a" int_0^"a" "f"(x)"d"x - 1`

or 1 = `"a"/2 int_0^"a" "f"(x)"d"x`

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Chapter 7: Integrals - Solved Examples [Page 160]

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NCERT Exemplar Mathematics [English] Class 12
Chapter 7 Integrals
Solved Examples | Q 24 | Page 160

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