1.

The differential equations, find a particular solution satisfying the given condition: `(dx)/(dy)+2ytanx=sinx ; y=0`when `x=pi/3`

Answer» Comparing the given equation with first order differential equation,
`dy/dx+Py = Q(x)`, we get,`P = 2tanx and Q(x) = sinx`
So, Integrating factor `(I.F) = e^(int2tanxdx)`
`I.F.= e^(2ln secx) = e^(ln sec^2x) = sec^2x`
We know, solution of differential equation,
`y(I.F.) = intQ(I.F.)dx`
`:.`Our solution will be,
`ysec^2x = int sinx(sec^2x)dx`
`=>ysec^2x = int sinx/cos^2xdx`
`=>ysec^2x = int tanx secx dx`
`=>ysec^2x =secx+c`
`=>y = cosx +c cos^2x`
At `x = pi/3, y=0`
`=>0 = 1/2 +c/4`
`=> -2 = c`
So, our solution will be,
`=>y = cosx - 2cos^2x`
`=>y = cosx(1-2cosx)`, which is the required solution.


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