If 2 + sin x d y d x + y + 1 cos x = 0 and y 0 = 1 , then y π 2 is equal to

If 2+sinxdydx+y+1cosx=0 and y0=1, then yπ2 is equal to
  1. 13
  2. -23
  3. -13
  4. 43

Solution

We have,

2+sinxdydx=-y+1cosx

dyy+1=-cosxsinx+2dx

Let, sinx=tcosxdx=dt

logy+1=-dtt+2+C

where, C is the constant of integration.

logy+1+logsinx+2-C=0

logy+1sinx+2=C

Given, y0=1

C=log4.

logy+1sinx+2=log4    .....i

Now, put x=π2 in the equation i, we get, logy+1+log3-log4=0

⇒ logy+1=log43

y+1=43

y=43-1=13.

Asked in: JEE Main 2017 (02 Apr)

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