JEE Main202429 Jan 2024Evening ShiftMathematicsDifferential EquationsActual
If sin y x = log e | x | + α 2 is the solution of the differential equation x cos y x d y d x = y cos y x + x and y ( 1 ) = π 3 , then α 2 is equal to
Options
- A3
- B12
- C4
- D9
Correct answer
A. 3
Step-by-step solution
Given: x cos y x d y d x = y cos y x + x ⇒ cos y x d y d x = y x cos y x + 1 Putting, y = v x ⇒ d y d x = v + x d v d x ⇒ cos v v + x d v d x = v cos v + 1 ⇒ v + x d v d x = v + 1 cos v ⇒ x d v d x = 1 cos v ⇒ cos v d v = d x x ⇒ ∫ cos v d v = ∫ d x x ⇒ sin v = log x + c ⇒ sin y x = log x + c Now, f 1 = π 3 ⇒ sin π 3 = log 1 + c ⇒ 3 2 = c ⇒ sin y x = log x + 3 2 So, on comparing we get, ⇒ α = 3 ⇒ α 2 = 3