1.

Consider the equation.\(\frac{dy}{dx}\) + y = sin xWhat is the order and degree of this equation?Find the integrating factor. Solve this equation.

Answer»

1. Order = 1, Degree = 1

2. Given,

 \(\frac{dy}{dx}\) + y = sin x is of the form

\(\frac{dy}{dx}\)+ Py = Q ⇒ P = 1, Q = sinx

Integrating factor = e∫Pdx = e∫1dx = ex

3. Therefore solution is

y.IF = ∫Q.IFdx + c ⇒ yex = ∫ex sinxdx + c ____(1)

∫sinx.exdx = ex sinx – ∫cosx.exdx

= ex sin x – cosx.ex – ∫sinx.ex dx

⇒ 2∫ex sin xdx = ex(sin x – cos x)

⇒ ∫ex sinxdx =\(\frac{e^x}{2}\)(sinx – cosx)

(1) ⇒ yex = \(\frac{e^x}{2}\)(sinx – cosx) + c.



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