NTA Abhyas JEE Main2020MathematicsDifferential EquationsPractice
If 2 + cos ⁡ x 3 + y d y d x + sin ⁡ x = 0 and y 0 = 1 , then y π 3 is equal to
Options
- A4 3
- B7 3
- C1 3
- D1
Correct answer
C. 1 3
Step-by-step solution
d y y + 3 = - sin ⁡ x 2 + cos ⁡ x d x ⇒ ln ⁡ y + 3 = ln ⁡ 2 + cos ⁡ x + ln ⁡ C ⇒ y + 3 = C ( 2 + cos ⁡ x ) Now, at x = 0 ,   y = 1 ⇒ 4 = 3 C ⇒ C = 4 3 ⇒ y = 4 3 2 + cos ⁡ x - 3 Hence, y π 3 = 4 3 2 + 1 2 − 3 = 2 3 ⋅ 5 − 3 = 1 3