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JEE Main202120 Jul 2021Evening ShiftMathematicsDifferential EquationsActual

Let y = y ( x ) satisfies the equation d y d x - A = 0 , for all x > 0 , where A = y sin x 1 0 - 1 1 2 0 1 x . If y ( π ) = π + 2 , then the value of y π 2 is:

Options

  1. Aπ 2 + 4 π
  2. Bπ 2 - 1 π
  3. C3 π 2 - 1 π
  4. Dπ 2 - 4 π

Correct answer

A. π 2 + 4 π

Step-by-step solution

We have, A = y sin x 1 0 - 1 1 2 0 1 x ⇒ A = - y x + 2 sin x + 2 Now, d y d x = A ⇒ d y d x = - y x + 2 sin x + 2 ⇒ d y d x + y x = 2 sin x + 2 I.F. = e ∫ 1 x d x = x Solution is y × I . F . = ∫ I . F . × 2 sin x + 2 d x ⇒ y x = ∫ x ( 2 sin x + 2 ) d x ⇒ y x = 2 ∫ x sin x d x + 2 ∫ x d x ⇒ x y = x 2 - 2 x cos x + 2 sin x + c       … i Now x = π ,   y = π + 2 , hence ⇒ π π + 2 = π 2 -

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